Resin composition for optical material, resin film for optical material, and optical waveguide

ABSTRACT

A resin composition for an optical material, which is excellent in heat resistance and transparency and is soluble in an aqueous alkali solution, a resin film for an optical material made of the resin composition, and an optical waveguide using the same are provided. The resin composition for an optical material includes: (A) an alkali-soluble (meth)acrylate polymer containing a maleimide skeleton in a main chain; (B) a polymerizable compound; and (C) a polymerization initiator. The resin film for an optical material is made of the resin composition for an optical material. The optical waveguide has a core part and/or a clad layer formed using the resin composition for an optical material or the resin film for an optical material.

This application is a Divisional application of application Ser. No.12/089,546, filed Apr. 8, 2008, which is a National Stage applicationfiled under 35 USC 371, of International (PCT) Application No.PCT/JP2007/064435, filed Jul. 23, 2007. The contents of No. 12/089,546are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a resin composition for an opticalmaterial, a resin film for an optical material, and an optical waveguideusing the same. In particular, the present invention relates to anoptical resin composition having excellent heat resistance andtransparency and is soluble in an aqueous alkaline solution, a resinfilm for an optical material made of the optical resin composition, andan optical waveguide using the same.

BACKGROUND ART

In recent years, in a high-speed and high-density signal transmissionbetween electronic devices or between wiring boards, the conventionaltransmission through electric wirings has began to reveal limitations inrealization of high speed and high density, because mutual interferenceand signal attenuation constitute barriers. In order to overcome suchlimitations, a technology for connecting between the electronic devicesor between the wiring boards by light, a so-called opticalinterconnection, is being examined. A polymer optical waveguide hasdrawn attention as an optical transmission path because of being easilyprocessed with low costs, greater wiring-flexibility, and high density.

As the modes of a polymer optical wave waveguide, it is considered thata type which is formed on a glass epoxy resin substrate on an assumptionof being applied onto a photoelectric consolidated substrate or aflexible type having no hard supporting substrate supposed to make aconnection between boards are preferred.

The polymer optical waveguide is also required to have high heatresistance in addition to have high transparency (low opticaltransmission loss) in terms of usage environment of an applicableapparatus, part implementation thereof, or the like. Known materials forthe optical wave guide include (meth)acrylate polymers (see, for examplePatent Documents 1 and 2).

However, even the (meth)acrylate polymers described in those patentdocuments have a high transparency of 0.3 dB/cm at a wavelength of 850nm, evaluation of heat resistance performance, for example, specifictest results such as optical transmission loss after a solder-reflowtest are not described in detail and thus unclear.

Patent Document 1: JP Hei 06-258537 A Patent Document 2: JP 2003-195079A DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been made for solving the above-mentionedproblems and aims to provide a resin composition for an optical materialhaving excellent heat resistance and transparency, and is soluble in anaqueous alkaline solution, a resin film for an optical material made ofthe resin composition, and an optical waveguide using the same.

Means for Solving the Problems

The inventors of the present invention have intensively studied, and asa result, they have found that the above-mentioned problems can besolved by producing: a resin composition for an optical materialincluding an alkali-soluble (meth)acrylate polymer having a maleimideskeleton in a main chain as a component (A) and also including acombination of (B) a polymerizable compound and (c) a polymerizationinitiator; and an optical waveguide using a resin film for an opticalmaterial made of the resin composition.

That is, the present invention provides a resin composition for anoptical material including: (A) an alkali-soluble (meta)acrylate polymercontaining a maleimide skeleton in a main chain; (B) a polymerizablecompound; and (C) a polymerization initiator, a resin film for anoptical material made of the resin composition for an optical material,and an optical waveguide in which at least one of a lower clad layer, acore part, and an upper clad layer is formed using the resin compositionfor an optical material or the resin film for an optical material.

Here, the (meth)acrylate polymers mean acrylate polymers and/or(meth)acrylate polymers.

EFFECT OF THE INVENTION

The resin composition for an optical material and the resin film for anoptical material made of the resin composition in accordance with thepresent invention are soluble in an aqueous alkali solution. The opticalwaveguide produced using the same is excellent in heat resistance andtransparency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional diagram illustrating a configuration of anoptical waveguide.

FIG. 2 is a graphic representation of a temperature profile in a reflowfurnace in a reflow test carried out in the present invention.

DESCRIPTION OF SYMBOLS

-   1 optical waveguide-   2 core part-   3 lower clad layer-   4 upper clad layer-   5 substrate

BEST MODE FOR CARRYING OUT THE INVENTION

The resin composition for an optical material of the present inventionpreferably be a resin composition to be hardened by heating orirradiation with an active light beam. The resin composition preferablyincludes (A) an alkali-soluble (meth) acrylate polymer having amaleimide skeleton in a main chain, (B) a polymerizable compound, and(C) a polymerization initiator.

Hereinafter, the component (A) used in the present invention will bedescribed.

The component (A), an alkali-soluble (meth)acrylate polymer having amaleimide skeleton in a main chain is not specifically limited as longas it can be dissolved in a developing solution made of an aqueousalkali solution and imparted with solubility enough to carry out adesired developing process. In terms of transparency, heat resistance,and solubility to an aqueous alkali solution, an alkali-soluble(meth)acrylate polymer is preferably used, the polymer including in themain chain repeating units (A-1) and (A-2) respectively represented bythe following general formulae (1) and (2) and at least one of repeatingunits (A-3) and (A-4) respectively represented by the following generalformulae (3) and (4).

where R¹ to R³ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms,

where R⁴ to R⁶ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms, and R⁷ represents anorganic group having 1 to 20 carbon atoms,

where R⁷ to R⁹ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms,

where R¹⁰ to R¹² and X¹ each independently represent any of a hydrogenatom and an organic group having 1 to 20 carbon atoms.

The organic groups represented by the general formulae (1) to (4)include, for example, monovalent or divalent groups, such as an alkylgroup, a cycloalkyl group, an aryl group, an aralkyl group, a carbonylgroup, an alkoxycarbonyl group, an aryloxy carbonyl group, and acarbamoyl group, which may be substituted with a hydroxyl group, ahalogen atom, an alkyl group, a cycloalkyl group, an aryl group, anaralkyl group, a carbonyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group alkoxy group, an aryloxy group, analkylthio group, an arylthio group, an amino group, a silyl group, orthe like.

In the alkali-soluble (meth)acrylate polymer having a maleimide skeletonin the main chain of the component (A), the content of the repeatingunit (A-1) derived from maleimide preferably fall in the range of 3 to50 mass %. If it is 3 mass % or more, heat resistance derived frommaleimide can be obtained. If it is 50 mass % or less, sufficienttransparency can be attained and a resulting resin pattern can be notfragile. In term of those facts, it is more preferably in the range of 5to 40 mass %, particularly preferably in the range of 10 to 30 mass %.

The structure of the repeating unit (A-1) derived from maleimide is notspecifically limited as long as it is represented by the general formula(1).

Examples of the maleimide serving as a raw material for the repeatingunit (A-1) include: alkylmaleimides such as N-methylmaleimide,N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide,N-butylmaleimide, N-isobutylmaleimide, N-2-methyl-2-propylmaleimide,N-pentylmaleimide, N-2-pentylmaleimide, N-3-pentylmaleimide,N-2-methyl-1-butylmaleimide, N-2-methyl-2-butylmaleimide,N-3-methyl-1-butylmaleimide, N-3-methyl-2-butylmaleimide,N-hexylmaleimide, N-2-hexylmaleimide, N-3-hexylmaleimide,N-2-methyl-1-pentylmaleimide, N-2-methyl-2-pentylmaleimide,N-2-methyl-3-pentylmaleimide, N-3-methyl-1-pentylmaleimide,N-3-methyl-2-pentylmaleimide, N-3-methyl-3-pentylmaleimide,N-4-methyl-1-pentylmaleimide, N-4-methyl-2-pentylmaleimide,N-2,2-dimethyl-1-butylmaleimide, N-3,3-dimethyl-1-butylmaleimide,N-3,3-dimethyl-2-butylmaleimide, N-2,3-dimethyl-1-butylmaleimide,N-2,3-dimethyl-2-butylmaleimide, N-hydroxymethylmaleimide,N-1-hydroxyethylmaleimide, N-2-hydroxyethylmaleimide,N-1-hydroxy-1-propylmaleimide, N-2-hydroxy-1-propylmaleimide,N-3-hydroxy-1-propylmaleimide, N-1-hydroxy-2-propylmaleimide,N-2-hydroxy-2-propylmaleimide, N-1-hydroxy-1-butylmaleimide,N-2-hydroxy-1-butylmaleimide, N-3-hydroxy-1-butylmaleimide,N-4-hydroxy-1-butylmaleimide, N-1-hydroxy-2-butylmaleimide,N-2-hydroxy-2-butylmaleimide, N-3-hydroxy-2-butylmaleimide,N-4-hydroxy-2-butylmaleimide, N-2-methyl-3-hydroxy-1-propylmaleimide,N-2-methyl-3-hydroxy-2-propylmaleimide,N-2-methyl-2-hydroxy-1-propylmaleimide, N-1-hydroxy-1-pentylmaleimide,N-2-hydroxy-1-pentylmaleimide, N-3-hydroxy-1-pentylmaleimide,N-4-hydroxy-1-pentylmaleimide, N-5-hydroxy-1-pentylmaleimide,N-1-hydroxy-2-pentylmaleimide, N-2-hydroxy-2-pentylmaleimide,N-3-hydroxy-2-pentylmaleimide, N-4-hydroxy-2-pentylmaleimide,N-5-hydroxy-2-pentylmaleimide, N-1-hydroxy-3-pentylmaleimide,N-2-hydroxy-3-pentylmaleimide, N-3-hydroxy-3-pentylmaleimide,N-1-hydroxy-2-methyl-1-butylmeleimide,N-1-hydroxy-2-methyl-2-butylmeleimide,N-1-hydroxy-2-methyl-3-butylmeleimide,N-1-hydroxy-2-methyl-4-butylmeleimide,N-2-hydroxy-2-methyl-1-butylmeleimide,N-2-hydroxy-2-methyl-3-butylmeleimide,N-2-hydroxy-2-methyl-4-butylmeleimide,N-2-hydroxy-3-methyl-1-butylmeleimide,N-2-hydroxy-3-methyl-2-butylmeleimide,N-2-hydroxy-3-methyl-3-butylmeleimide,N-2-hydroxy-3-methyl-4-butylmeleimide,N-4-hydroxy-2-methyl-1-butylmeleimide,N-4-hydroxy-2-methyl-2-butylmeleimide,N-1-hydroxy-3-methyl-2-butylmeleimide,N-1-hydroxy-3-methyl-1-butylmeleimide,N-1-hydroxy-2,2-dimethyl-1-propylmaleimide,N-3-hydroxy-2,2-dimethyl-1-propylmaleimide,N-1-hydroxy-1-hexylmaleimide, N-1-hydroxy-2-hexylmaleimide,N-1-hydroxy-3-hexylmaleimide, N-1-hydroxy-4-hexylmaleimide,N-1-hydroxy-5-hexylmaleimide, N-1-hydroxy-6-hexylmaleimide,N-2-hydroxy-1-hexylmaleimide, N-2-hydroxy-2-hexylmaleimide,N-2-hydroxy-3-hexylmaleimide, N-2-hydroxy-4-hexylmaleimide,N-2-hydroxy-5-hexylmaleimide, N-2-hydroxy-6-hexylmaleimide,N-3-hydroxy-1-hexylmaleimide, N-3-hydroxy-2-hexylmaleimide,N-3-hydroxy-3-hexylmaleimide, N-3-hydroxy-4-hexylmaleimide,N-3-hydroxy-5-hexylmaleimide, N-3-hydroxy-6-hexylmaleimide,N-1-hydroxy-2-methyl-1-pentylmaleimide,N-1-hydroxy-2-methyl-2-pentylmaleimide,N-1-hydroxy-2-methyl-3-pentylmaleimide,N-1-hydroxy-2-methyl-4-pentylmaleimide,N-1-hydroxy-2-methyl-5-pentylmaleimide,N-2-hydroxy-2-methyl-1-pentylmaleimide,N-2-hydroxy-2-methyl-2-pentylmaleimide,N-2-hydroxy-2-methyl-3-pentylmaleimide,N-2-hydroxy-2-methyl-4-pentylmaleimide,N-2-hydroxy-2-methyl-5-pentylmaleimide,N-2-hydroxy-3-methyl-1-pentylmaleimide,N-2-hydroxy-3-methyl-2-pentylmaleimide,N-2-hydroxy-3-methyl-3-pentylmaleimide,N-2-hydroxy-3-methyl-4-pentylmaleimide,N-2-hydroxy-3-methyl-5-pentylmaleimide,N-2-hydroxy-4-methyl-1-pentylmaleimide,N-2-hydroxy-4-methyl-2-pentylmaleimide,N-2-hydroxy-4-methyl-3-pentylmaleimide,N-2-hydroxy-4-methyl-4-pentylmaleimide,N-2-hydroxy-4-methyl-5-pentylmaleimide,N-3-hydroxy-2-methyl-1-pentylmaleimide,N-3-hydroxy-2-methyl-2-pentylmaleimide,N-3-hydroxy-2-methyl-3-pentylmaleimide,N-3-hydroxy-2-methyl-4-pentylmaleimide,N-3-hydroxy-2-methyl-5-pentylmaleimide,N-1-hydroxy-4-methyl-1-pentylmaleimide,N-1-hydroxy-4-methyl-2-pentylmaleimide,N-1-hydroxy-4-methyl-3-pentylmaleimide,N-1-hydroxy-3-methyl-1-pentylmaleimide,N-1-hydroxy-3-methyl-2-pentylmaleimide,N-1-hydroxy-3-methyl-3-pentylmaleimide,N-1-hydroxy-3-methyl-4-pentylmaleimide,N-1-hydroxy-3-methyl-5-pentylmaleimide,N-3-hydroxy-3-methyl-1-pentylmaleimide,N-3-hydroxy-3-methyl-2-pentylmaleimide,N-1-hydroxy-3-ethyl-4-butylmaleimide,N-2-hydroxy-3-ethyl-4-butylmaleimide,N-2-hydroxy-2-ethyl-1-butylmaleimide,N-4-hydroxy-3-ethyl-1-butylmaleimide,N-4-hydroxy-3-ethyl-2-butylmaleimide,N-4-hydroxy-3-ethyl-3-butylmaleimide,N-4-hydroxy-3-ethyl-4-butylmaleimide,N-1-hydroxy-2,3-dimethyl-1-butylmaleimide,N-1-hydroxy-2,3-dimethyl-2-butylmaleimide,N-1-hydroxy-2,3-dimethyl-3-butylmaleimide,N-1-hydroxy-2,3-dimethyl-4-butylmaleimide,N-2-hydroxy-2,3-dimethyl-1-butylmaleimide,N-2-hydroxy-2,3-dimethyl-3-butylmaleimide,N-2-hydroxy-2,3-dimethyl-4-butylmaleimide,N-1-hydroxy-2,2-dimethyl-1-butylmaleimide,N-1-hydroxy-2,2-dimethyl-3-butylmaleimide,N-1-hydroxy-2,2-dimethyl-4-butylmaleimide,N-2-hydroxy-3,3-dimethyl-1-butylmaleimide,N-2-hydroxy-3,3-dimethyl-2-butylmaleimide,N-2-hydroxy-3,3-dimethyl-4-butylmaleimide,N-1-hydroxy-3,3-dimethyl-1-butylmaleimide,N-1-hydroxy-3,3-dimethyl-2-butylmaleimide, andN-1-hydroxy-3,3-dimethyl-4-butylmaleimide; cycloalkylmaleimides such asN-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclopentylmaleimide,N-cyclohexylmaleimide, N-cycloheptylmaleimide, N-cyclooctylmaleimide,N-2-methylcyclohexylmaleimide, N-2-ethylcyclohexylmaleimide, andN-2-chlorocyclohexylmaleimide; and arylmaleimides such asN-phenylmaleimide, N-2-methylphenylmaleimide, N-2-ethylphenylmaleimide,and N-2-chlorophenylmaleimide.

Of those, a cycloalkylmaleimide is preferably used, andN-cyclohexylmaleimide and N-2-methylcyclohexylmaleimide are morepreferably used from the viewpoint of the transparency and solubility.

Those compounds may be used alone or in combination of two or more.

In the alkali-soluble (meth)acrylate polymer having a maleimide skeletonin the main chain of the component (A), the content of the repeatingunit (A-2) derived from (meth)acrylate is preferably in the range of 20to 90 mass %. If it is 20 mass % or more, transparency derived from(meth)acrylate can be obtained. If it is 90 mass % or less, sufficientheat resistance can be attained. From the above viewpoint, a range of 25to 85 mass % is more preferred and a range of 30 to 80 mass % isparticularly preferred.

The structure of the repeating unit (A-2) derived from (meth) acrylateis not specifically limited as long as it is represented by the generalformula (2).

Examples of the (meth)acrylate serving as a raw material for therepeating unit (A-2) include: aliphatic (meth)acrylates such asmethyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate,isobutyl(meth)acrylate, tert-butyl(meth)acrylate,butoxyethyl(meth)acrylate, isoamyl(meth)acrylate, hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, heptyl(meth)acrylate,octylheptyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate,undecyl(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate,tetradecyl(meth)acrylate, pentadecyl(meth)acrylate,hexadecyl(meth)acrylate, stearyl(meth)acrylate, behenyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,3-chloro-2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate,methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol(meth)acrylate, methoxypolypropyleneglycol (meth)acrylate,ethoxypolypropyleneglycol (meth)acrylate, andmono(2-(meth)acryloyloxyethyl)succinate; alicyclic (meth)acrylates suchas cyclopentyl(meth)acrylate, cyclohexyl(meth)acrylate,dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate,isobornyl(meth)acrylate,mono(2-(meth)acryloyloxyethyl)tetrahydrophthalate, andmono(2-(meth)acryloyloxyethyl)hexahydrophthalate; aromatic(meth)acrylates such as benzyl(meth)acrylate, phenyl(meth)acrylate,o-biphenyl(meth)acrylate, 1-naphthyl(meth)acrylate,2-naphthyl(meth)acrylate, phenoxyethyl(meth)acrylate,p-cumylphenoxyethyl(meth)acrylate, o-phenylphenoxyethyl(meth)acrylate,1-naphthoxyethyl(meth)acrylate, 2-naphthoxyethyl(meth)acrylate,phenoxypolyethyleneglycol (meth)acrylate, nonylphenoxypolyethyleneglycol(meth)acrylate, pehnoxypolypropyleneglycol (meth)acrylate,2-hydroxy-3-phenyoxypropyl (meth)acrylate,2-hydroxy-3-(o-phenylphenoxy)propyl (meth)acrylate,2-hydroxy-3-(1-naphthoxy)propyl (meth)acrylate, and2-hydroxy-3-(2-naphthoxy)propyl (meth)acrylate; heterocyclic(meth)acrylates such as 2-tetrahydroflufuryl(meth)acrylate,N-(meth)acryloyloxyethylhexahydrophthal imide, and2-(meth)acryloyloxyethyl-N-carbazole; and caprolatone-modified compoundsthereof.

Of those, in terms of transparency and heat resistance, (meth) acrylatespreferably include: aliphatic (meth)acrylates, such as methyl(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and2-ethylhexyl (meth)acrylate; the above alicyclic (meth) acrylates; theabove aromatic (meth)acrylates; and the above heterocyclic(meth)acrylates.

Those compounds may be used independently or in combination of two ormore thereof.

In the alkali-soluble (meth)acrylate polymer having a maleimide skeletonin the main chain of the component (A), the content of the repeatingunits (A-3) and (A-4) derived from compounds having a carboxyl group andan unsaturated ethylenic double bond is preferably in the range of 3 to60 mass %. If it is 3% mass or more, the component (A) can be easilydissolved in a developing solution, such as an aqueous alkali solution.If it is 60 mass % or less, anti-developer property (the nature of aportion which is not removed by development and remained as a pattern isnot affected by a developing solution) is good in the developing processfor selectively removing a photosensitive resin composition layer toform a pattern by development as described later. From the aboveviewpoints, the content is more preferably in the range of 5 to 50 mass%, particularly preferably in the range of 10 to 40 mass %.

The structures of the repeating units (A-3) and (A-4) derived fromcompounds having a carboxyl group and an ethylenic unsaturated group arenot specifically limited as long as they are represented by the generalformulae (3) and (4), respectively.

Compounds each having a carboxyl group and an ethylenic unsaturatedgroup and serving as raw materials for the repeating unit (A-3) include,for example, (meth) acrylic acid, maleic acid, fumaric acid, crotonicacid, itaconic acid, citraconic acid, mesaconic acid, and cinnamic acid.Of those, in terms of transparency and alkaline solubility, (meth)acrylic acid, maleic acid, fumaric acid, and crotonic acid arepreferred.

Further, maleic anhydride may be used as a raw material and polymerized,followed by ring-opening with appropriate alcohol, such as methanol,ethanol, or propanol, thereby converting to the structure of therepeating unit (A-3).

Those compounds can be used independently or in combination of two ormore thereof.

Examples of the compound serving as a raw material for the repeatingunit (A-4) and having a carboxyl group and an ethylene unsaturated groupinclude mono (2-(meth)acryloyloxyethyl)succinate,mono(2-(meth)acryloyloxyethyl)phthalate,mono(2-(meth)acryloyloxyethyl)isophthalate,mono(2-(meth)acryloyloxyethyl)terephthalate,mono(2-(meth)acryloyloxyethyl)tetrahydrophthalate,mono(2-(meth)acryloyloxyethyl)hexahydrophthalte,mono(2-(meth)acryloyloxyethyl)hexahydroisophthalate,mono(2-(meth)acryloyloxyethyl)hexahydroterephthalate,ω-carboxy-polycaprolactone mono(meth)acrylate, 3-vinylbenzoate, and4-vinylbenzoate.

Of those, mono(2-(meth)acryloyloxyethyl)succinate,mono(2-(meth)acryloyloxyethyl)tetrahydrophthalate,mono(2-(meth)acryloyloxyethyl)hexahydrophthalate,mono(2-(meth)acryloyloxyethyl)hexahydroisophthalate, andmono(2-(meth)acryloyloxyethyl)hexahydroterephthalate are preferred fromthe viewpoint of transparency and alkali solubility.

Those compounds can be used independently or in combination of two ormore thereof.

In addition, the alkali-soluble (meth)acrylate polymer having amaleimide skeleton in the main chain of the component (A) may include anadditional repeating structure other than the repeating structures (A-1)to (A-4) if required.

Examples of the compounds having ethylenic unsaturated groups andserving as raw materials for such repeating structures include, but notspecifically limited to, styrene, α-methyl styrene, vinyl toluene, vinylchloride, vinyl acetate, vinyl pyridine, N-vinyl pyrrolidine, N-vinylcarbazole, butadiene, isoprene, and chloroprene. Of those, in terms ofheat resistance and transparency, styrene, α-methyl styrene, vinyltoluene, and N-vinyl carbazole are preferably used.

Those compounds can be used independently or in combination of two ormore thereof.

The synthesis method for the alkali-soluble (meth) acrylate polymerhaving a maleimide skeleton in the main chain of the component (A) isnot specifically limited. It may be obtained by copolymerization ofmaleimide as a raw material for the repeating unit (A-1), (meth)acrylateas a raw material for the repeating unit (A-2), and a compound having acarboxyl group and an ethylenic unsaturated group as a raw material forthe repeating unit (A-3) and/or the repeating unit (A-4), and optionallyany of other compounds having ethylenic unsaturated groups while beingheated using a thermal radical polymerization initiator. In this case,if required, an organic solvent may be used as a reaction solvent.

Examples of the thermal radical polymerization initiator are notlimited, and include: ketone peroxides such as methylethyl ketoneperoxide, cyclohexanone peroxide, methylcyclohexanone peroxide;peroxyketals such as 1,1-bis(t-butylperoxy)cyclohexane,1,1-bis(t-butylperoxy)-2-methylcyclohexane,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-hexylperoxy)cyclohexane, and1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane; hydroperoxides suchas p-methane hydroperoxide; dialkyl peroxides such as α,α′-bis(t-butylperoxy)diisopropylbenzene, dicumylperoxide, t-butylcumylperoxide, and di-t-butyl peroxide; diacylperoxides such as octanoylperoxide, lauroyl peroxide, stearyl peroxide, and benzoyl peroxide;peroxycarbonates such as bis(4-t-butylcyclohexyl)peroxydicarbonate,di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate,and di-3-methoxybutyl peroxycarbonate; peroxyesters such as t-butylperoxypivalate, t-hexyl peroxypivalte,1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate,2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate,t-butylperoxyisobutyrate, t-hexylperoxyisopropyl monocarbonate,t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurylate,t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-butylperoxybenzoate, t-hexylperoxybenzoate,2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyacetate; and azocompounds such as 2,2′-azobis(isobutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile), and2,2′-azobis(4-methoxy-2′-dimethylvaleronitrile).

The organic solvent used as the reaction solvent is not limited as longas the organic solvent can dissolve the alkali soluble (meth)acrylatepolymer having a maleimide skeleton in the main chain of (A) component.Examples of the organic solvent include: aromatic hydrocarbons such astoluene, xylene, mesitylene, cumene, and p-cymene; cyclic ethers such astetrahydrofurane and 1,4-dioxane; alcohols such as methanol, ethanol,isopropanol, butanol, ethylene glycol, and propylene glycol; ketonessuch as acetone, methylethyl ketone, methylisobutyl ketone,cyclohexanone, 4-hydroxy-4-methyl-2-pentanone; esters such as methylacetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate,and γ-butyrolactone; carbonates such as ethylene carbonate and propylenecarbonate; polyalcohol alkylethers such as ethyleneglycolmonomethylether, ethyleneglycol monoethylether, ethyleneglycolmonobutylether, ethyleneglycol dimethylether, ethyleneglycoldiethylether, propyleneglycol monomethylether, propyleneglycolmonoethylether, propyleneglycol dimethylether, propyleneglycoldiethylether, diethyleneglycol monomethylether, diethyleneglycolmonoethylether, diethyleneglycol monobutylether, diethyleneglycoldimethylether, and diethyleneglycol diethylether; polyalcohol alkyletheracetates such as ethyleneglycol monomethylether acetate, etheyleneglycolmonoethylether acetate, ethyleneglycol monobutylether acetate,propyleneglycol monomethylether acetate, propyleneglycol monoethyletheracetate, diethyleneglycol monomethylether acetate, and diethyleneglycolmonoethylether acetate; amides such as N,N-dimethylformamide,N,N-dimethylacetamide, and N-methylpyrrolidone.

Those organic solvents may be used singly or two or more thereof may beused in combination.

Further, the alkali-soluble (meth)acrylate polymer having a maleimideskeleton in the main chain of the component (A) may contain an ethylenicunsaturated group on the side chain thereof if required. Its compositionand synthetic method are not specifically limited. For example, theabove (meth)acrylate polymer can be provided with an ethylenicunsaturated group on its side chain by an addition reaction of acompound having at least one ethylenic unsaturated group and onefunctional group, such as an epoxy group, an oxycetanyl group, anisocyanate group, a hydroxyl group, or a carboxyl group.

Examples of the compounds are not limited, and include: compounds eachhaving an ethylene unsaturated group and an epoxy group, such asglycidyl(meth)acrylate, α-ethylglycidyl(meth)acrylate,α-propylglycidyl(meth)acrylate, α-butylglycidyl(meth)acrylate,2-methylglycidyl(meth)acrylate, 2-ethylglycidyl(meth)acrylate,2-propylglycidyl(meth)acrylate, 3,4-epoxybutyl(meth)acrylate,3,4-epoxyheptyl(meth)acrylate, α-ethyl-6,7-epoxyheptyl(meth)acrylate,3,4-epoxycyclohexylmethyl(meth)acrylate, o-vinylbenzylglycidyl ether,m-vinylbenzylglycidyl ether, and p-vinylbenzylglycidyl ether; compoundshaving an ethylene unsaturated group and an oxetanyl group, such as(2-ethyl-2-oxetanyl)methyl(meth)acrylate,(2-methyl-2-oxetanyl)methyl(meth)acrylate,2-(2-ethyl-2-oxetanyl)ethyl(meth)acrylate,2-(2-methyl-2-oxetanyl)ethyl(meth)acrylate,3-(2-ethyl-2-oxetanyl)propyl(meth)acrylate, and3-(2-methyl-2-oxetanyl)propyl(meth)acrylate; compounds having anethylene unsaturated group and an isocyanate group, such as2-(meth)acryloyloxyethyl isocyanate; compounds having an ethyleneunsaturated group and a hydroxyl group, such as2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,3-chloro-2-hydroxypropyl(meth)acrylate, and2-hydroxybutyl(meth)acrylate; and compounds having an ethyleneunsaturated group and a carboxyl group, such as (meth) acrylic acid,crotonic acid, cinnamic acid, (2-(meth)acryloyloxyethyl)succinate,2-phthaloylethyl(meth)acrylate, 2-tetrahydrophthaloylethyl(meth)acrylate, 2-hexahydrophthaloylethyl (meth)acrylate,ω-carboxyl-polycaprolactone mono (meth)acrylate, 3-vinylbenzoate, and4-vinylbenzoate.

Of those, glycidyl(meth)acrylate,3,4-epoxycyclohexylmethyl(meth)acrylate, isocyanic acidethyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, (meth)acrylic acid, crotonic acid, and 2-hexahydrophthaloylethyl(meth)acrylate are preferred from the viewpoint of the transparency andreactivity.

Those organic solvents may be used singly or two or more thereof may beused in combination.

The average molecular weight of the alkali-soluble (meth)acrylatepolymer having a maleimide skeleton in the main chain in the component(A) is preferably in the range of 1,000 to 3,000,000. If it is 1,000 ormore, a large molecular weight leads to a sufficient strength of ahardened product in the case of using as a resin composition. If it is3,000,000 or less, it leads to good solubility to a developing solutionmade of an aqueous alkali solution and compatibility to thepolymerizable compound (B). From the view point of the abovedescription, a molecular weight of 3,000 to 2,000,000 is more preferred.A molecular weight of 5,000 to 1,000,000 is particularly preferred.

Note that the weight average molecular weight in the present inventionis a value determined by measurement by gel permeation chromatography(GPC) and calculation in terms of standard polystyrene.

The acid value of the alkali-soluble (meth)acrylate polymer having amaleimide skeleton in the main chain in the component (A) can be definedso that development can be attained using any of various knowndeveloping solutions in the process of forming pattern by selectivelyremoving a photosensitive resin composition layer by the development asdescribed later. For instance, in the case of the development with anaqueous alkali solution of sodium carbonate, potassium carbonate,tetramethyl ammonium hydroxide, triethanolamine, or the like, the acidvalue is preferably in the range of 20 to 300 mgKOH/g. If it is 20mgKOH/g or more, the development can be easily carried out. If it is 300mgKOH/g or less, there is no decrease in anti-developer property. Fromthe viewpoint of the above description, a range of 30 to 250 mgKOH/g ismore preferred. A range of 40 to 200 mgKOH/g is particularly preferred.

In the case of developing with an aqueous alkali solution made of wateror an aqueous alkali solution and one or more of surfactants, the acidvalue thereof is preferably in the range of 10 to 260 mgKOH/Hg. If theacid value is 10 mgKOH/g or more, the development can be easilyperformed. If it is 260 mgKOH/g or less, there is no decrease inanti-developer property. From the viewpoint of the above description, arange of 20 to 250 mgKOH/g is more preferred. A range of 30 to 200mgKOH/g is particularly preferred.

The blending amount of the component (A) is preferably 10 to 85 mass %with respect to the total mass of the components (A) and (B). If it is10 mass % or more, a hardened product of the resin composition for anoptical material has sufficient strength and plasticity. If it is 85mass % or less, the component (A) may be tangled with the component (B)and easily hardened when exposed. Thus, there is no lack ofanti-developer property. From the viewpoint of the above description, arange of 20 to 80 mass % is more preferred. A range of 25 to 75 mass %is particularly preferred.

Hereinafter, the component (B) used in the present invention will bedescribed.

The polymerizable compound of the component (B) is not specificallylimited as long as it can be polymerized by heating, UV irradiation, orthe like. Examples of such a compound preferably include compoundshaving polymerizable substituents, such as ethylenic unsaturated groups.

Specifically, the compounds include: (meth)acrylate, vinylidene halide,vinyl ether, vinyl ester, vinyl pyridine, vinyl amide, and arylatedvinyl. Of those, in terms of transparency, (meth) acrylate and arylatedvinyl are preferred. The (meth)acrylate may be any of monofunctional,difunctional, or polyfunctional (meth) acrylate.

Examples of the monofunctional (meth)acrylate include: aliphatic(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate,butyl(meth)acrylate, isobutyl(meth)acrylate, tert-butyl(meth)acrylate,butoxyethyl(meth)acrylate, isoamyl(meth)acrylate, hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, heptyl(meth)acrylate,octylheptyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate,undecyl(meth)acrylate, lauryl(meth)acrylate, tridecyl(meth)acrylate,tetradecyl(meth)acrylate, pentadecyl(meth)acrylate,hexadecyl(meth)acrylate, stearyl(meth)acrylate, behenyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate,3-chloro-2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate,methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol(meth)acrylate, methoxypolypropyleneglycol(meth)acrylate,ethoxypolypropyleneglycol(meth)acrylate,mono(2-(meth)acryloyloxyethyl)succinate; alicyclic (meth)acrylates suchas cyclohexyl(meth)acrylate, cyclopentyl(meth)acrylate,dicyclopentanyl(meth)acrylate, dicyclopentenyl(meth)acrylate,isobornyl(meth)acrylate,mono(2-(meth)acryloyloxyethyl)tetrahydrophthalate, andmono(2-(meth)acryloyloxyethyl)hexahydrophthalate; aromatic(meth)acrylates such as benzyl(meth)acrylate, phenyl(meth)acrylate,o-biphenyl(meth)acrylate, 1-naphthyl(meth)acrylate,2-naphthyl(meth)acrylate, phenoxyethyl(meth)acrylate,p-cumylphenoxyethyl(meth)acrylate, o-phenylphenoxyethyl(meth)acrylate,1-naphthoxyethyl(meth)acrylate, 2-naphthoxyethyl(meth)acrylate,phenoxypolyethyleneglycol (meth)acrylate, nonylphenoxypolyethyleneglycol(meth)acrylate, pehnoxypolypropyleneglycol (meth)acrylate,2-hydroxy-3-phenoxypropyl(meth)acrylate,2-hydroxy-3-(o-phenylphenoxy)propyl(meth)acrylate,2-hydroxy-3-(1-naphthoxy)propyl(meth)acrylate, and2-hydroxy-3-(2-naphthoxy)propyl(meth)acrylate; heterocyclic(meth)acrylates such as 2-tetrahydroflufuryl(meth)acrylate,N-(meth)acryloyloxyethylhexahydrophthal imide, and2-(meth)acryloyloxyethyl-N-carbazole; and caprolatone-modified compoundsthereof.

Of those, the alicyclic (meth)acrylates, the aromatic (meth)acrylates,and the heterocyclic (meth)acrylates are preferred from the viewpoint ofthe transparency and reactivity.

Examples of the bifunctional (meth)acrylate include: aliphatic(meth)acrylates such as ethyleneglycol di(meth)acrylate,diethyleneglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate,tetraethyleneglycol di(meth)acrylate, polyethyleneglycoldi(meth)acrylate, propyleneglycol di(meth)acrylate, dipropyleneglycoldi(meth)acrylate, tripropyleneglycol di(meth)acrylate,tetrapropyleneglycol di(meth)acrylate, polypropyleneglycoldi(meth)acrylate, ethoxylated polypropyleneglycol di(meth)acrylate,1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate,neopentylglycol di(meth)acrylate, 3-methyl-1,5-pentanedioldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate,2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 1,9-nonanedioldi(meth)acrylate, 1,10-decanediol di(meth)acrylate, glycerinedi(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, andethoxylated 2-methyl-1,3-propanediol di(meth)acrylate; alicyclic(meth)acrylates such as cyclohexanedimethanol (meth)acrylate,ethoxylated cyclohexanedimethanol (meth)acrylate, propoxylatedcyclohexanedimethanol (meth)acrylate, ethoxylated propoxylatedcyclohexanedimethanol (meth)acrylate, tricyclodecanedimethanol(meth)acrylate, ethoxylated tricyclodecanedimethanol (meth)acrylate,propoxylated tricyclodecanedimethanol (meth)acrylate, ethoxylatedpropoxylated tricyclodecanedimthanol (meth)acrylate, ethoxylatedhydrogenated bisphenol A di(meth)acrylate, propoxylated hydrogenatedbisphenol A di(meth)acryalte, ethoxylated propoxylated hydrogenatedbisphenol A di(meth)acryalte, ethoxylated hydrogenated bisphenol Fdi(meth)acrylate, propoxylated hydrogenated bisphenol Fdi(meth)acrylate, and ethoxylated propoxylated hydrogenated bisphenol Fdi(meth)acrylate; aromatic (meth)acrylates such as ethoxylated bisphenolA di(meth)acrylate, propoxylated bisphenol A di(meth)acrylate,ethoxylated propoxylated bisphenol A di(meth)acrylates, ethoxylatedbisphenol F di(meth)acrylate, propoxylated bisphenol F di(meth)acrylate,ethoxylated propoxylated bisphenol F di(meth)acrylate, ethoxylatedbisphenol AF di(meth)acrylate, propoxylated bisphenol AFdi(meth)acrylate, ethoxylated propoxylated bisphenol AFdi(meth)acrylate, ethoxylated fluorene-type di(meth)acrylate,propoxylated fluorene-type di(meth)acrylate, and ethoxylatedpropoxylated fluorene-type di(meth)acrylate; heterocyclic(meth)acrylatessuch as ethoxylated isocyanuric acid di(meth)acrylate, propoxylatedisocyanuric acid di(meth)acrylate, and ethoxylated propoxylatedisocyanuric acid di(meth)acrylate; caprolactone-modified compoundsthereof; aliphatic epoxy (meth)acrylates such as neopentylglycol-typeepoxy(meth)acrylate; alicyclic epoxy(meth)acrylates such ascyclohexanedimethanol-type epoxy(meth)acrylate, hydrogenated bisphenolA-type epoxy(meth)acrylate, and hydrogenated bisphenol F-typeepoxy(meth)acrylate; aromatic epoxy (meth)acrylates such asresorcinol-type epoxy(meth)acrylate, bisphenol A-typeepoxy(meth)acrylate, bisphenol F-type epoxy(meth)acrylate, bisphenolAF-type epoxy(meth)acrylate, and fluorene-type epoxy(meth)acrylate.

Of those, the alicyclic (meth)acrylates, the aromatic (meth)acrylates,the heterocyclic (meth)acrylates, the alicyclic epoxy(meth)acrylates,and the aromatic epoxy(meth)acrylates are preferred from the viewpointof the transparency and heat resistance.

Examples of polyfunctional (meth)acrylate having a trifunctional groupor more include: aliphatic (meth)acrylates such as trimethylolpropanetri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate,propoxylated trimethylolpropane tri(meth)acrylate, ethoxylatedpropoxylated trimethylolpropane tri(meth)acrylate, pentaerythritoltri(meth)acrylate, ethoxlated pentaerythritol tri(meth)acrylate,propoxylated pentaerythritol tri(meth)acrylate, ethoxylated propoxylatedpentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,ethoxylated pentaerythritol tetra(meth)acrylate, propoxylatedpentaerythritol tetra(meth)acrylate, ethoxylated propoxylatedpentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetraacrylate,and dipentaerythritol hexa(meth)acrylate; heterocyclic (meth)acrylatessuch as ethoxylated isocyanuric acid tri(meth)acrylate, propoxylatedisocyanuric acid tri(meth)acrylate, and ethoxylated propoxylatedisocyanuric acid tri(meth)acrylate; caprolactone-modified compoundsthereof; aromatic epoxy(meth)acrylates such as phenol novolac-typeepoxy(meth)acrylate and cresol novolac-type epoxy(meth)acrylate.

Of those, the heterocyclic (meth)acrylates and aromaticepoxy(meth)acrylates are preferred from the viewpoint of thetransparency and heat resistance.

Those compounds may be used independently or in combination of two ormore thereof. Further, they may be used in combination with any of otherpolymerizable compounds.

In addition, in terms of heat resistance, the polymerizable compound ofthe component (B) used is preferably one or more compounds eachcontaining in molecule: an ethylenic unsaturated group; and at least oneselected from the group consisting of an alicyclic structure, an arylgroup, an aryl oxy group, and an aralkyl group. Specifically, itincludes (meth)acrylate, N-vinyl carbazole, or the like each containingat least one selected from the group consisting of an alicyclicstructure, an aryl group, an aryl oxy group, and an aralkyl group. Here,the term “aryl group” represents an aromatic carbonate group such as aphenyl group and a naphthyl group, and an aromatic heterocyclic groupsuch as a carbazole group.

More specifically, the polymerizable compound of the component (B) usedis preferably at least one of compounds represented by the followinggeneral formulae (5) to (8). Alternatively, the polymerizable compoundof the component (B) used is more preferably at least one of compoundscontaining an aryl group and an ethylenic unsaturated group representedby the following general formulae (5) to (8).

where Ar represents any of the following groups

X² represents any of divalent groups of an oxygen atom (O), a sulfuratom (S), OCH₂, SCH₂, O(CH₂CH₂O)_(a), O(CH₂CH₃O)_(b),O[CH₂CH(CH₃)O]_(b), OCH₂CH(OH)CH₂O;

Y¹ represents any of the following divalent groups

R¹³ represents any of a hydrogen atom and a methyl group;

R¹⁴ to R³⁰ each independently represent a hydrogen atom, a fluorineatom, an organic group having 1 to 20 carbon atoms, and afluorine-containing organic group having 1 to 20 carbon atoms; and

a and b each independently represent an integer of 1 to 20 and crepresents an integer of 2 to 10).

where R³¹ represents any of the following groups

R³² to R³⁴ each independently represent any of a hydrogen atom and amethyl group; and d represents an integer of 1 to 10.

where X³ and X⁴ each independently represent any of divalent groups ofO, S, O(CH₂CH₂O)_(e), and 0[CH₂CH(CH₃)O]_(f);

Y² represents any of the following divalent groups

R³⁵ and R⁴⁰ each independently represent any of a hydrogen atom and amethyl group; R³⁶ to R³⁹ each represent a hydrogen atom, a fluorineatom, an organic group having 1 to 20 carbon atoms, and afluorine-containing organic group having 1 to 20 carbon atoms; and e andf each independently represent an integer of 1 to 20 and g represents aninteger of 2 to 10.

where Y³ represents any of the following divalent groups

R⁴¹ and R⁴⁶ each independently represent any of a hydrogen atom and amethyl group; R⁴² to R⁴⁵ each independently represent a hydrogen atom, afluorine atom, an organic group having 1 to 20 carbon atoms, and afluorine-containing organic group having 1 to 20 carbon atoms; and hrepresents an integer of 1 to 5 and i represents an integer of 2 to 10.

Here, examples of the organic groups in the general formulae (5) to (8)include those described in the general formulae (1) to (4).

In addition, preferable polymerizable compounds (B) other than(meth)acrylate include compounds each having two or more epoxy groups inmolecule in terms of compatibility to the alkali-soluble (meth)acrylatepolymer (A) having a maleimide skeleton in a main chain.

Specific examples thereof include: bifunctional phenol glycidyl etherssuch as a bisphenol A type epoxy resin, a tetrabromobisphenol A typeepoxy resin, a bisphenol F type epoxy resin, a bisphenol AF type epoxyresin, a bisphenol AD type epoxy resin, a biphenyl type epoxy resin, anaphthalene type epoxy resin, and a fluorene type epoxy resin;hydrogenated bifunctional phenol glycidyl ethers such as a hydrogenatedbisphenol A type epoxy resin, a hydrogenated bisphenol F type epoxyresin, a hydrogenated 2,2′-bisphenol type epoxy resin, and ahydrogenated 4,4′-bisphenol type epoxy resin; polyfunctional phenolglycidyl ethers such as a phenol novolak type epoxy resin, a cresolnovolak type epoxy resin, a dicyclopentadiene-phenol type epoxy resin,and a tetraphenylolethane type epoxy resin; bifunctional aliphaticalcohol glycidyl ethers such as a polyethylene glycol type epoxy resin,a polypropylene glycol type epoxy resin, a neopentyl glycol type epoxyresin, and a 1,6-hexanediol type epoxy resin; bifunctional alicyclicalcohol glycidyl ethers such as a cyclohexane dimethanol type epoxyresin and a tricyclodecane dimethanol type epoxy resin; polyfunctionalaliphatic alcohol glycidyl ethers such as a trimethylolpropane typeepoxy resin, a sorbitol type epoxy resin, and a glyceine type epoxyresin; bifunctional aromatic glycidyl esters such as diglycidylphthalate; bifunctional alicyclic glycidyl esters such as diglycidyltetrahydrophthalate and diglycidyl hexahydrophthalate; bifunctionalaromatic glycidylamines such as N,N-diglycidylaniline andN,N-diglycidyltrifluoromethylaniline; polyfunctional aromaticglycidylamines such asN,N,N′,N′-tetraglycidyl-4,4-diaminodiphenylmethane,1,3-bis(N,N-glycidylaminomethyl)cyclohexane, andN,N,O-triglycidyl-p-aminophenol; bifunctional alicyclic epoxy resinssuch as alicyclic diepoxy acetal, alicyclic diepoxy adipate, alicyclicdiepoxy carboxylate, and vinyl cyclohexene dioxide; polyfunctionalalicyclic epoxy resins such as 1,2-epoxy-4-(2-oxiranyl)cyclohexaneadducts of 2,2-bis(hydroxymethyl)-1-butanol; polyfunctional heterocyclicepoxy resins such as triglycidyl isocyanurate; and bifunctional orpolyfunctional silicon-containing epoxy resins such as anorganopolysiloxane type epoxy resin.

Of those, in terms of transparency and heat resistance, specificexamples of the epoxy resins include: bifunctional phenol glycidylethers, such as a bisphenol A type epoxy resin, a bisphenol F type epoxyresin, a bisphenol AF type epoxy resin, a bisphenol AD type epoxy resin,a biphenyl type epoxy resin, a naphthalene type epoxy resin, and afluorene type epoxy resin; the above hydrogenerated bifunctional phenolglycidyl ethers; the above polyfunctional phenol glycidyl ethers; theabove bifunctional alicyclic alcohol glycidyl ethers; the abovebifunctional aromatic glycidyl ethers; the above bifunctional alicyclicglycidyl ethers; the above bifunctional alicyclic epoxy resin; the abovepolyfunctional alicyclic epoxy resin; the above polyfunctionalheterocyclic epoxy resin; and the above silicon-containing bifunctionalor polyfunctional epoxy resin.

Those compounds may be used independently or in combination of two ormore thereof. Further, they may be used in combination of any of otherpolymerizable compounds.

The blending amount of the polymerizable compound of the component (B)is preferably 15 to 90 mass % with respect to the total mass of thecomponents (A) and (B). If it is 15 mass % or more, the alkali-soluble(meth)acrylate polymer (A) having a maleimide skeleton in the main chainmay be tangled with the component (B) and easily hardened when exposed.Thus, there is no lack of anti-developer property. In addition, if it is90 mass % or less, the film strength and the plasticity of the hardenedfilm may be sufficient. From the viewpoint of the above description, arange of 30 to 80 mass % is more preferred.

Hereinafter, the component (C) used in the present invention will bedescribed.

The polymerization initiator of the component (C) is not particularlylimited as long as it can allow polymerization to start by heating, UVirradiation, or the like. For instance, in the case of using a compoundhaving an ethylenic unsaturated group as a polymerizable compound of thecomposition (B), examples of the polymerization initiator include athermal radical polymerization initiator and a photoradicalpolymerization initiator. Of those, the photoradical polymerizationinitiator is preferred because of its possibility to be hardened at anormal temperature at a high hardening rate.

Examples of the thermal radical polymerization initiator include: ketoneperoxides such as methylethyl ketone peroxide, cyclohexanone peroxide,and methylcyclohexanone peroxide; peroxyketals such as1,1-bis(t-butylperoxy)cyclohexane,1,1-bis(t-butylperoxy)-2-methylcyclohexane,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-hexylperoxy)cyclohexane, and1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane; hydroperoxides suchas p-methane hydroperoxide; dialkyl peroxides such as α,α′-bis(t-butylperoxyl)diisopropylbenzene, dicumylperoxide, t-butylcumylperoxide, and di-t-butyl peroxide; diacylperoxides such as octanoylperoxide, lauroyl peroxide, stearyl peroxide, and benzoyl peroxide;peroxycarbonates such as bis(4-t-butylcyclohexy)peroxydicarbonate,di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate,and di-3-methoxybutyl peroxycarbonate; peroxyesters such as t-butylperoxypivalate, t-hexyl peroxypivalte,1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate,2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane,t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate,t-butylperoxyisobutyrate, t-hexylperoxyisopropyl monocarbonate,t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurylate,t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexylmonocarbonate, t-butylperoxybenzoate, t-hexylperoxybenzoate,2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, and t-butylperoxyacetate; andazo compounds such as 2,2′-azobis(isobutylonitrile),2,2′-azobis(2,4-dimethylvaleronitrile), and2,2′-azobis(4-methoxy-2′-dimethylvaleronitrile).

Of those, the diacylperoxides, the peroxyesters, and the azo compoundsare preferred from the viewpoint of curing property, transparency, andheat resistance.

Examples of the photoradical polymerization initiator include: benzoinketals such as 2,2-dimethoxy-1,2-diphenylethane-1-one; α-hydroxy ketonessuch as 1-hydroxycyclohexylphenyl ketone,2-hydroxy-2-methyl-1-phenylpropane-1-one and1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one;α-amino ketones such as2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1-one, and1,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one; oximeesters such as1-[(4-phenylthio)phenyl]-1,2-octanedione-2-(benzoyl)oxime; phosphineoxides such as bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and2,4,6-trimethylbenzoyldiphenylphosphineoxide; 2,4,5-triarylimidazoledimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer,2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, and2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer; benzophenone compoundssuch as benzophenone, N,N′-tetramethyl-4,4′-diaminobenzophenone,N,N′-tetramethyl-4,4′-diaminobenzophenone, and4-methoxy-4′-dimethylaminobenzophenone; quinone compounds such as2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone,octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone,2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone,2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone,2-methyl-1,4-naphthoquinone, and 2,3-dimethylanthraquinone; benzoinethers such as benzoinmethyl ether, benzomethyl ether, and benzoinphenylether; benzoin compounds such as benzoin, methylbenzoin, andethylbenzoin; benzyl compounds such as benzyldimethyl ketal; acridinecompounds such as 9-phenylacridine, 1,7-bis(9,9′-acridinylheptane);N-phenylglycine; and cumarine.

Further, in the above 2,4,5-triaryl imidazole dimer, the substituents ofthe aryl groups at two triaryl imidazole portions may be identicalsymmetrical compounds or may be different dissymmetric compounds. Inaddition, like a combination of diethyl thioxanthone anddimethylaminobenzoic acid, a thioxanthone compound and a tertiary aminemay be combined together.

Of those, in terms of hardenability, transparency, and heat resistance,the above α-hydroxyl ketone and the above phosphine oxide are preferred.These thermal and photoradical polymerization initiators may be usedindependently or in combination of two or more thereof. Further, it maybe also used in combination with an appropriate sensitizer.

Further, in the case of using an epoxy resin as a polymerizable compoundof the component (B), the polymerization initiator of the component (C)may be a thermal cationic polymerization initiator, a photocationicpolymerization initiator, or the like. Of those, the photocationicpolymerization initiator is preferred because of its possibility to behardened at a normal temperature at a high hardening rate.

Examples of the thermal cation polymerization initiator include:benzylsulfonium salts such as p-alkoxyphenylbenzylmethylsulfoniumhexafluoroantimonate; pyridinium salts such as benzyl-p-cyanopyridiniumhexafluoroantimonate, 1-naphthylmethyl-o-cyanopyridiniumhexafluoroantiomoate, and cinnamyl-o-cyanopyridiniumhexafluoroantimonate; benzylammonium salts such asbenzyldimethylphenylammonium hexafluoroantimonate.

Of those, the benzylsulfonium salts is preferred from the viewpoint ofcuring property, transparency, and heat resistance.

Examples of the photo cation polymerization initiator include:diaryldiazonium salts such as p-methoxybenzenediazoniumhexafluorophosphate; diaryliodonium salts such as diphenyliodoniumhexafluorophosphate and diphenyliodonium hexafluoroantiomonate;triarylsulfonium salts such as triphenylsulfonium hexafluorophosphate,triphenylsulfonium hexafluoroantimonate,diphenyl-4-thiophenoxyphenylsulfonium hexafluorophosphate,diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate, anddiphenyl-4-thiophenoxyphenylsulfonium pentafluorohydroxyantimonate;triarylselenium salts such as triphenylselenium hexafluorophosphate,triphenylselenium tetrafluoroborate, and triphenylseleniumhexafluoroantimonate; dialkylphenacylsulfonium salts such asdimethylphenacylsulfonium hexafluoroantimonate, anddiethylphenacylsulfonium hexafluoroantimonate; dialkyl-4-hydroxyl saltssuch as 4-hydroxyphenyldimethylsulfonium hexafluoroantimonate and4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate; andphosphates such as α-hydroxymethylbenzoyl sulfonate, N-hydroxyimidesulfonate, α-sulfonyloxy ketone, and β-sulfonyloxy ketone.

Of those, in terms of hardenability, transparency, and heat resistance,the above triaryl sulfonium salt is preferred. These thermal andphotocationic polymerization initiators may be used independently or incombination of two or more thereof. Further, it may be also combinedwith an appropriate sensitizer.

The blending amount of the polymerization initiator of the component (C)is preferably 0.1 to 10 parts by mass with respect of 100 parts by massof the component (A) and the component (B) in total. If it is 0.1 partby mass or more, the hardening may be sufficient. If it is 10 parts bymass or less, sufficient optical transparency may be obtained. From theviewpoint of the above description, a range of 0.3 to 7 parts by mass ismore preferred. A range of 0.5 to 5 parts by mass is particularlypreferred.

If required, further, the resin composition for an optical material ofthe present invention may be further added with a so-called additive,such as an antioxidant, an yellowing inhibitor, a UV absorber, avisible-light absorbent, a coloring agent, a plasticizer, a stabilizer,or a filler, in such a ratio that it does not adversely affect theeffects of the present invention.

Hereinafter, the resin composition for an optical material of thepresent invention will be described.

The resin composition for an optical material of the present inventionmay be diluted with a favorable organic solvent and then used as a resinvarnish for an optical material. The organic solvent used herein is notparticularly limited as long as the resin composition can be dissolvedtherein. Examples of the organic solvent include: aromatic hydrocarbonssuch as toluene, xylene, mesitylene, cumene, and p-cymene; cyclic etherssuch as tetrahydrofuran and 1,4-dioxane; alcohols such as methanol,ethanol, isopropanol, butanol, ethyleneglycol, and propylene glycol;ketones such as acetone, methylethyl ketone, methylisobutyl ketone,cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methylacetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate,and γ-butyrolactone; carbonates such as ethylene carbonate and propylenecarbonate; polyalcohol alkylethers such as ethyleneglycol monomethylether, ethyleneglycol monoethyl ether, ethyleneglycol monobutyl ether,ethyleneglycol dimethyl ether, ethyleneglycol diethyl ether,propyleneglycol monomethyl ether, propyleneglycol monoethyl ether,propyleneglycol dimethyl ether, propyleneglycol diethyl ether,diethyleneglycol monomethyl ether, diethyleneglycol monoethyl ether,diethyleneglycol monobutyl ether, diethyleneglycol dimethyl ether, anddiethyleneglycol diethyl ether; polyalcohol alkylether acetates such asethyleneglycol monomethylether acetate, etheyleneglycol monoethyletheracetate, ethyleneglycol monobutylether acetate, propyleneglycolmonomethylether acetate, propyleneglycol monoethylether acetate,diethyleneglycol monomethylether acetate, and diethyleneglycolmonoethylacetate; amides such as N,N-dimethylformamide,N,N-dimethylacetamide, and N-methylpyrrolidone.

Of those, toluene, methanol, ethanol, isopropanol, acetone, methylethylketone, methylisobutyl ketone, cyclohexanone, methyl acetate, ethylacetate, butyl acetate, methyl lactate, ethyl lactate, ethyleneglycolmonomethylether, ethyleneglycol monoethylether, propyleneglycolmonomethylether, propyleneglycol monoethylether, diethyleneglycoldimethylether, ethyleneglycol monomethylether acetate, propyleneglycolmonomethyl ether acetate, and N,N-dimethylacetamide are preferred fromthe viewpoint of the solubility and boiling point.

Those organic solvents may be used singly or two or more thereof may beused in combination.

In general, further, the concentration of a solid in the resin varnishis preferably 20 to 80 mass %.

When a resin varnish for an optical material is prepared, mixing ispreferably carried out by agitation. An agitation method is, but notspecifically limited to, preferably agitation with a propeller in termsof agitation efficiency. The rotational speed of the propeller is, butnot specifically limited to, preferably 10 to 1,000 rpm. If it is 10 rpmor more, each of the components (A) to (C) and the organic solvent canbe sufficiently mixed with one another. If it is 1,000 rpm or less, thedegree of sucking air bubbles into the mixture by the rotation of thepropeller is lowered. From the above viewpoint, a range of 50 to 800 rpmis more preferred. A range of 100 to 500 rpm is particularly preferred.The stirring time is, but not specifically limited to, preferably 1 to24 hours. If it is 1 hour or more, each of the components (A) to (C) andthe organic solvent can be sufficiently mixed with one another. If it is24 hours or less, the time required for preparing the varnish can beshortened.

The prepared resin varnish for an optical material is preferablyfiltrated through a filter with a pore size of 50 μm or less. If thepore size is 50 μm or less, larger foreign materials or the like can beremoved. Thus, the scattering of light passing through a core part canbe prevented without repelling when the varnish is applied. From theabove viewpoint, a filter having a pore size of 30 μm or less is morepreferably used in the filtration. A filter having a pore size of 10 μmor less is particularly preferably used in the filtration.

The prepared resin varnish for an optical material is preferablysubjected to defoaming under reduced pressure. A defoaming method is notspecifically limited. As a specific example, a vacuum pump and a glassbell jar, or a defoaming apparatus with a vacuum device can be used. Thepressure at the time of pressure reduction is, but not specificallylimited to, preferably a pressure at which an organic solvent in theresin varnish does not boil. The time for defoaming under reducedpressure is, but not specifically limited to, preferably 3 to 60minutes. If it is 3 minutes or more, air bubbles dissolved in the resinvarnish can be removed. If it is 60 minutes or less, an organic solventin the resin varnish will not vaporize.

A hardened film obtained by polymerization and hardening of a resincomposition for an optical material including the alkali-soluble(meth)acrylate polymer having a maleimide skeleton in the main chain ofthe component (A), the polymerizable compound (B), and thepolymerization initiator (C) has a refractive index of 1.400 to 1.700 ata wavelength of 830 nm at a temperature of 25° C. If it is in the rangeof 1.400 to 1.700, there is no increase in the refractive index with theusual optical resin. Thus, the versatility of the hardened film as anoptical material is not spoiled. From the above viewpoint, therefractive index is more preferably 1.425 to 1.675 or less, particularlypreferably 1.450 to 1.650.

A hardened film with a thickness of 50 μm, which is obtained bypolymerization and hardening of a resin composition for an opticalmaterial including the alkali-soluble (meth)acrylate polymer having amaleimide skeleton in the main chain of the component (A), thepolymerizable compound (B), and the polymerization initiator (C),preferably has a transmissivity of 80% or more at a wavelength of 400nm. If it is 80% or more, the amount of the transmitted light issufficient. From the above viewpoint, 85% or more is more preferred.Note that the upper limit of the transmissivity is not specificallylimited.

Hereinafter, the resin film for an optical material of the presentinvention will be described.

The resin film for an optical material of the present invention is madeof the above resin composition for an optical material. It can be easilymanufactured by a process in which a resin varnish for an opticalmaterial including the compositions (A) to (C) is applied on a favorablebase material film and a solvent is then removed therefrom.Alternatively, it may be manufactured by directly applying the resincomposition for an optical material on a base material film.

Examples of the base material film are not particularly limited, andinclude: polyesters such as polyethyleneterephthalate,polybutyleneterephthalate, and polyethylenenaphthalate; polyolefins suchas polyethylene and polypropylene; polycarbonate; polyamide; polyimide;polyamideimide; polyetherimide; polyethersulfide; polyethersulfone;polyetherketone; polyphenylether; polyphenylenesulfide; polyallylate;polysulfone; and liquid crystal polymer. Of those,polyetheyleneterephthalate, polybutyleneterephthalate,polyethethylenenaphthalate, polypropylene, polycarbonate, polyamide,polyimide, polyamideimide, polyphenylenether, polyphenylenesulfide,polyarylate, and polysulfone are preferred from the viewpoint of theflexibility and high toughness.

The thickness of the base material film may be arbitrarily changeddepending on the desired flexibility, but is preferably in the range of3 to 250 μm. If it is 3 μm or more, the film may be provided withsufficient strength. If it is 250 μm or less, the film may be providedwith sufficient flexibility. From the above viewpoint, the thickness ismore preferably 5 to 200 μm, particularly preferably 7 to 150 μm. Fromthe viewpoint of an improvement of detachability from a resin layer, afilm used may be one subjected to a mold-release treatment with asilicon compound, a fluorine-containing compound, or the like ifrequired.

The resin film for an optical material manufactured by applying a resinvarnish for an optical material or a resin composition for an opticalmaterial on a base material film may be optionally constructed of athree-layered structure: a base material film, a resin layer, and aprotective film, which protective film being attached on the resin film.

Examples of the protective film include: but not specifically limitedto, polyesters, such as polyethylene terephthalate, polybutyleneterephthalate, and polyethylene naphthalate; and polyolefins, such aspolyethylene and polypropylene. Of those, in terms of flexibility andtoughness, polyesters, such as polyethylene terephthalate; andpolyolefins, such as polyethylene and polypropylene, are preferred.Here, in terms of an improvement of detachability from the resin layer,a film used may be one subjected to a mold-release treatment with asilicon compound, a fluorine-containing compound, or the like ifrequired. The thickness of a cover film may be properly changeddepending on the desired flexibility, but is preferably in the range of10 to 250 μm. If it is 10 μm or more, the film is provided withsufficient strength. If it is 250 μm or less, the film is provided withsufficient flexibility. From the above viewpoint, the thickness of thefilm is more preferably 15 to 200 μm, particularly preferably 20 to 150μm.

The thickness of the resin layer of the resin film for an opticalmaterial of the present invention is not specifically limited. However,the thickness of the resin layer after drying is, in general, preferably5 to 500 μm. If it is 5 μm or more, the thickness of the resin layer issufficient enough to provide the resin film or a hardened productthereof with sufficient strength. If it is 500 μm or less, the dryingcan be sufficiently carried out. Thus, the amount of the remainingsolvent in the resin film does not increase and foaming does not occurwhen the hardened product of the film is heated.

The resin film for an optical material thus obtained can be easilystored by, for example, taking up in a roll form. Alternatively, thefilm in the roll form may be cut into pieces with suitable dimensionsand then stored in a sheet form.

The resin composition for an optical material of the present inventionis suitable for a resin composition for the formation of an opticalwaveguide. Similarly, the resin film for an optical material of thepresent invention is suitable for a resin film for the formation of anoptical waveguide.

Hereinafter, the optical waveguide of the present invention will bedescribed.

FIG. 1( a) represents a cross-sectional view of an optical waveguide.The optical waveguide 1 is formed on a substrate 5 and constructed of acore part 2 made of a resin composition for core part formation with ahigh refractive index, and a lower clad layer 4 and an upper clad layer3 made of a resin composition for clad layer formation with a lowrefractive index.

The resin composition for an optical material and the resin film for anoptical material in accordance with the present invention are preferablyused in at least one of the lower clad layer 4, the core part 2, and theupper clad layer 3 of the optical waveguide 1. Of those, from theviewpoint of the ability of pattern forming by a developing solutionmade of an aqueous alkali solution, it is more preferable to be used inat least the core part 2 among them.

The use of a resin film for an optical material can lead to a furtherincrease in adhesiveness between the clad layer and the core layer andthe ability of forming a pattern (ability of responding to the spacingbetween thin lines or narrow lines), thereby enabling the fine patternformation with a small line width or line spacing. In addition, itbecomes possible to provide a process with excellent productivity thatcan produce large-area optical waveguide at once.

In an optical waveguide 1, a substrate 5 used may be a hard substrate,such as a glass-epoxy resin substrate including a silicon substrate, aglass substrate and a FR-4 substrate. The optical waveguide 1 may be aflexible optical waveguide using the above flexible and tough basematerial film instead of the above substrate.

In addition, when the base material film having flexibility andtoughness is used as the substrate 5, the substrate 5 may be functionedas a cover film of the optical waveguide 1. The arrangement of the coverfilm 5 can impart the flexibility and toughness of the cover film 5 tothe optical waveguide 1. Therefore, the optical waveguide 1 can beprevented from contamination and blemish, so that it can be handled moreeasily.

From the above viewpoint, as shown in FIG. 1( b), the cover film 5 maybe arranged on the outside of the upper clad layer 3. Alternatively, asshown in FIG. 1( c), the cover film 5 may be arranged on the outsides ofboth the lower clad layer 3 and the upper clad layer 3.

As long as the optical waveguide 1 is sufficiently provided withflexibility and toughness, the cover film 5 may not be arranged as shownin FIG. 1( d).

The thickness of the low clad layer 4 is, but not specifically limitedto, preferably 2 to 200 μm. If it is 2 μm or more, the transmissionlight can be easily confined in the inside of the core. If it is 200 μmor less, the thickness of the optical waveguide 1 is not out of anallowable range. Here, the term “thickness of the low clad layer 4”means a distance from the boundary between the core part 2 and the lowerclad layer 4 to the lower surface of the clad layer 4.

The thickness of the resin film for the formation of a low clad layer isnot specifically limited, but it can be adjusted so that the thicknessof the lower clad layer 4 after the hardening may be within the aboverange.

The height of the core part 2 is, but not specifically limited to,preferably within the range of 10 to 100 μm. If the core part has aheight of 10 μm or more, the tolerance of alignment for the binding tolight-receiving and light-emitting elements or an optical fiber afterthe formation of the optical waveguide does not decrease. If thetolerance is 100 μm or less, the binding efficiency for the binding tolight-receiving and light-emitting elements or an optical fiber afterthe formation of the optical waveguide does not decrease. From the aboveviewpoint, the height of the core part is more preferably 15 to 80 μm,particularly preferably 20 to 70 μm. Further, the thickness of the resinfilm for the formation of a core part is not particularly limited andcan be adjusted so that the height of the core portion after thehardening may be within the above range.

The thickness of the upper clad layer 3 is not specifically limited aslong as it is within the range that allows the core part 2 to beembedded therein, but is preferably 12 to 500 μm after it is dried. Thethickness of the upper clad layer 3 may be identical with or differentfrom the thickness of the lower clad layer 4 formed at first. In termsof embedding the core part 2, the thickness of the upper clad layer 3 ispreferably higher than that of the lower clad layer 4. Note that theterm “thickness of the upper clad layer 3” means a distance from theboundary between the core part 2 and the lower clad layer 4 to the uppersurface of the upper clad layer 3.

The optical waveguide of the present invention preferably has preferablyan optical transmission loss of 0.3 dB/cm or less. If the opticaltransmission loss is 0.3 dB or less, the loss of light is small and thestrength of a transmission signal is thus sufficient. From the aboveview point, 0.2 dB/cm or less is more preferred.

In addition, the optical waveguide of the present invention preferablyhas an optical transmission loss of 0.3 dB/cm or less after carrying outa reflow test three times at a maximum temperature of 265° C. If it is0.3 dB/cm or less, the loss of light is small and the strength of atransmission signal is sufficient while the component mounting with areflow process can be carried out. Thus, it can be widely applied. Here,the term “reflow test at a maximum temperature of 265° C.” means alead-free solder reflow test carried out under conditions according toJEDEC standard (JEDEC JESD22A113E).

Hereinafter, an application example of using the resin film for anoptical material of the present invention as a resin film for theformation of an optical waveguide, which is the most suitable usethereof, will be described.

The resin film for the formation of an optical waveguide can be alsomanufactured in a manner similar to that of manufacturing the aboveresin film for an optical material. By the way, a substrate used in theprocess of manufacturing the resin film for forming a core part is notspecifically limited as long as the substrate allows exposure activelight used in the core-pattern formation as described later to passtherethrough. Examples of the substrate include: polyethylenes, such aspolyethylene terephthalate, polybutylene terephthalate, and polyethylenenaphthalate; polyolefines, such as polyethylene and polypropylene;polycarbonates; polyphenylene ethers; and polyarylates.

Of those, in the viewpoint of transmissivity, flexibility, and toughnessof the exposure active light, polyesters, such as polyethyleneterephthalate and polybutylene terephthalate, and polyolefines, such aspolypropylene, are preferred. Further, in the viewpoint of an increasein transmissivity of the exposure active light and a decrease inroughness of the side wall of a core pattern, it is more preferable touse a high-transparent type base material film. Such a high-transparenttype base material film includes Cosmo Shine A1517 and Cosmo ShineA4100, which are manufactured by Toyobo Co., Ltd. Here, in terms of anincrease in detachability from the resin layer, any film subjected to amold-releasing treatment with a silicon-based compound, afluorine-containing compound, or the like may be used as necessary.

The thickness of the base material film of the resin film for theformation of a core part is preferably 5 to 50 μm. If it is 5 μm ormore, sufficient strength as a substrate can be obtained. If it is 50 μmor less, an increase in size of the gap between a photomask and theresin composition layer for the formation of a core pattern does notoccur when the core pattern is formed. Thus, it results in a goodproperty of forming a pattern. From the above viewpoint, the thicknessof the base material film is more preferably 10 to 40 μm, particularlypreferably 15 to 30 μm.

The resin film for the formation of an optical waveguide, which ismanufactured by applying a resin varnish for the formation of an opticalwaveguide or a resin composition for the formation of an opticalwaveguide on the above base material film, may be optionally of athree-layered structure constructed of a base material film, a resinfilm, and a protective film, which protective film being attached on theresin film if required.

The resin film for the formation of an optical waveguide thus obtainedcan be easily stored by being taken up in a roll form. Alternatively,the film in the roll form may be cut into pieces with suitabledimensions and then stored in a sheet form.

Hereinafter, a method of forming an optical waveguide 1 using a resinvarnish for the formation of an optical waveguide and/or a resin filmfor the formation of an optical waveguide will be described.

The method of manufacturing the optical waveguide 1 of the presentinvention may be, but not specifically limited to, a method that carriesout the production by a spin-coating method or the like using a resinvarnish for the formation of a core part and a resin varnish for theformation of a clad layer, a method that carries out the production by alamination method using a resin film for the formation of a core partand a resin film for the formation of a clad layer or the like.Alternatively, it may be manufactured by a combination of those methods.Of those, in terms of a possibility to provide a process formanufacturing an optical waveguide with excellent productivity, themethod that carries out the production by a lamination method using theresin film for the formation of an optical waveguide is preferred.

Hereinafter, a manufacturing method of forming an optical waveguide 1 inwhich a resin film for the formation of an optical waveguide is used ina lower clad layer, a core part, and an upper clad layer.

At first, as a first step, a lower clad layer 4 is formed by laminatinga resin film for the formation of a lower clad layer on a substrate 5.The lamination method in the first step may be a method of laminating bypressure-bonding with heat using a roll laminator or a flat-platelaminator. In terms of adhesion and followability, it is preferable touse a flat-plate laminator for laminating a resin film for the formationof a lower clad layer under reduced pressure. In the present invention,the term “flat-plate laminator” means a laminator for press-bonding suchthat lamination materials are sandwiched between a pair of flat platesand pressure is then applied on the flat plates. For example, avacuum-pressure type laminator can be preferably used. The heatingtemperature used herein is preferably 40 to 130° C. The pressure atwhich pressure-bonding is performed is preferably 0.1 to 1.0 MPa.However, there is no limitation in those conditions. In the case of thepresence of a protective film on the resin film for the formation of alower clad layer, the lamination is carried out after removing theprotective film.

Alternatively, before laminating by the vacuum-pressure type laminator,the resin film for the formation of a lower clad layer may betemporarily attached on the substrate 5 using the roll lamination. Here,for the viewpoint of improving adhesion and followability, the temporalattachment may be preferably performed while subjecting topress-bonding. The press-binding may be carried out using a laminatorhaving a heat roll under heat. The lamination temperature is preferably20 to 130° C. In other words, 20° C. or more leads to an increase inadhesion between the resin film for the formation of a lower clad layerand the substrate 5. If it is 130° C. or less, a required film thicknesscan be obtained without causing an excessive flow of a resin layer atthe time of roll lamination. From the above viewpoint, the laminationtemperature is more preferably 40 to 100° C. The pressure is preferably0.2 to 0.9 MPa. The lamination rate is preferably 0.1 to 3 m/min.However, there is no limitation in those conditions.

Subsequently, the resin film for the formation of a lower clad layerlaminated on the substrate 5 is hardened by application of light and/orheat to remove the base material film from the resin film for theformation of a lower clad layer, thereby forming a lower clad layer 4.

For the formation of the lower clad layer 4, the irradiation dose ofactive light beam is preferably 0.1 to 5 J/cm² and the heatingtemperature is preferably 50 to 200° C. However, there is no limitationin those conditions.

Then, as a second step, a resin film for the formation of a core part islaminated in a manner similar to that of the first step. Here, the resinfilm for the formation of a core part is preferably designed so that therefractive index thereof is higher than that of the resin film for theformation of a lower clad layer and preferably made of a photosensitiveresin composition capable of forming a core pattern by active lightbeam.

Next, as a third step, the core part is exposed to form a core pattern(core part 2) of the optical waveguide. Specifically, an active lightbeam may be applied through a negative or positive mask pattern calledartwork so that it forms an image. Alternatively, the active light beammay be directly by laser direct-drawing so that it forms an imagewithout passing through a photomask. Examples of the light source foractive light beam include known light sources that can effectivelyradiate ultraviolet ray, for example, a carbon arc lamp, a mercury vaporarc lamp, a super-high pressure mercury lamp, a high pressure mercurylamp, and a Xenon lamp. Besides, those light sources that effectivelyradiate visible light, such as a flood lamp for photography and asunlight lamp, can also be used.

The irradiation amount of active light beam used herein is preferably0.01 to 10 J/cm². The range is preferable because, if it is 0.01 J/cm²or more, a hardening reaction proceeds sufficiently and the core part 2is not flown out in the step of development as described later and, ifit is 10 J/cm² or less, a fine pattern can be formed without an increasein thickness of the core part 2 by an excess amount of exposure. Fromthe above viewpoint, the irradiation amount of active light beam is morepreferably 0.05 to 5 J/cm², particularly preferably 0.1 to 3 J/cm².

Alternatively, in terms of improving the resolution and adhesion of thecore part 2, the application of heat may be performed after theexposure. The time period from the irradiation of UV and the applicationof heat after the exposure is preferably within 10 minutes. If it iswithin 10 minutes, an active species generated by the UV irradiation isnot deactivated. The temperature of the heating after the exposure ispreferably 40 to 160° C. and the time period thereof is preferably 30seconds to 10 minutes.

After the exposure, the base material film of the resin film for theformation of a core part is removed. Then, the development is carriedout by a known method, such as spray, oscillating dipping, brushing,scrapping, dipping, and puddling, using a developing liquid thatcorresponds to the composition of the above resin film for the formationof a core part, such as an alkaline aqueous solution or a water-baseddeveloping agent. Alternatively, if required, two or more kinds of thedeveloping methods may be used in combination.

The bases that can be used for the above-mentioned alkaline aqueoussolution include, but are not limited to, for example: alkali hydroxidessuch as hydroxides of lithium, sodium, and potassium; alkali carbonatessuch as carbonates or bicarbonates of lithium, sodium, potassium, andammonium; alkali metal phosphates such as potassium phosphate, andsodium phosphate; alkali metal pyrophosphates such as sodiumpyrophosphate and potassium pyrophosphate; sodium salts such as boraxand sodium metasilicate; and organic bases such as tetramethyl ammoniumhydroxide, triethanolamine, ethylenediamine, diethylenetriamine,2-amino-2-hydroxymethyl-1,3-propandiol and1,3-diaminopropanol-2-morpholine. Further, it is preferable that thealkaline aqueous solutions for development have a pH in the range of 9to 11. The temperature of the alkaline aqueous solution is adjusteddepending on the developability of the layer of the resin compositionfor forming core-part. The alkaline aqueous solutions may containsurfactants, defoaming agents, a small amount of organic solvent forpromoting development, and the like.

The above water-based developing solution is not specifically limited aslong as it may be made of: water or an aqueous alkali solution; and oneor more organic solvents. The pH of the water-based developing solutionis preferably as small as possible within in a range at which thedevelopment of the resin film for the formation of a core part can besufficiently performed, more preferably pH 8 to 12, particularlypreferably pH 9 to 10.

Examples of the organic solvent include: alcohols such as methanol,ethanol, isopropanol, butanol, ethyleneglycol, and propylene glycol;ketones such as acetone, and 4-hydroxy-4-methyl-2-pentanone; andpolyalcohol alkylethers such as ethyleneglycol monomethylether,ethyleneglycol monoethylether, propyleneglycol monomethylether,propyleneglycol monoethylether, diethyleneglycol monomethylether,diethyleneglycol monoethylether, and diethyleneglycol monobutylether.

These organic solvents may be used independently or in combination oftwo or more thereof. In general, the concentration of the organicsolvent is preferably 2 to 90 mass % and the temperature thereof isadjusted depending on the developability of the resin composition forthe formation of a core part. In addition, the water-based developingsolution may contain a small amount of a surfactant, a defoaming agent,or the like.

As the treatment after the development, the core part 2 of the opticalwaveguide may be washed with a washing solution made of water and theabove organic solvent if required. The organic solvents may be usedindependently or in combination of two or more thereof. In general, theconcentration of the organic solvent is preferably 2 to 90 mass %. Thetemperature thereof may be adjusted so as to correspond to thedevelopability of the resin composition for the formation of a corepart.

As the treatment after the development, heating at about 60 to 250° C.or exposure to about 0.1 to 1,000 mJ/cm² may be performed as necessaryto further harden the core part 2.

Then, as a fourth step, a resin film for the formation of an upper cladlayer is laminated in the same manner as those of the first and secondsteps to form an upper clad layer 3. Here, the resin film for theformation of the upper clad layer is designed so that the refractiveindex thereof can be smaller than that of the resin film for theformation of a core part. In addition, the thickness of the upper cladlayer 3 may be preferably larger than the height of the core part 2.

Subsequently, in a manner similar to that of the first step, the resinfilm for the formation of an upper clad layer is hardened by lightand/or heat to form an upper clad layer 3.

If the base material film of the resin film for the formation of a cladlayer is made of PET, the irradiation amount of active light beam ispreferably 0.1 to 5 J/cm². On the other hand, if the base material filmis made of polyethylene naphthalate, polyamide, polyimide,polyamidoimide, polyetherimide, polyphenylene ether, polyether sulfide,polyether sulfone, or polysulfone, it hardly allow an active light beam,such as UV, with a short wavelength to pass through the base materialfilm compared with PET. Thus, the active light beam has preferably anirradiation amount of 0.5 to 30 J/cm². A hardening reaction proceedssufficiently when the irradiation amount is 0.5 J/cm² or more. The lightirradiation does not take much time when the irradiation amount is 30J/cm² or less. From the above viewpoint, the irradiation amount ispreferably 3 to 27 J/cm², more preferably 5 to 25 J/cm².

Alternatively, for more hardening, a double-side exposure device capableof simultaneously irradiating from both sides with active beams may beused. In addition, the irradiation of active light beam may be carriedout under heating. The heating temperature during and/or after theirradiation of active light beam may be preferably 50 to 200° C.However, there is no limitation in those conditions.

Alternatively, the optical waveguide 1 may be prepared by removing thebase material film, if required, after forming the upper clad layer 3.

The optical waveguide of the present invention is excellent in heatresistance and transparency, so that it may be used as an opticaltransmission of an optical module. The configuration of the opticalmodule may be, for example, an optical waveguide provided with opticalfibers connected to both ends of the optical waveguide; an opticalwaveguide provided with connectors connected to both ends of the opticalwaveguide; a photoelectric composite substrate in which an opticalwaveguide is in complex with a print-wiring board; aphotoelectric-converting module in which an optical waveguide iscombined with a photoelectric-converting device for mutual conversionbetween an optical signal and an electric signal; or awavelength-division-multiplexing device in which an optical waveguide iscombined with a wavelength-division filter. Here, in the photoelectriccomposite substrate, the print wiring plate to be complex may be, butnot specifically limited to, either of rigid substrates, such as a glassepoxy substrate, and flexible substrates, such as a polyimide substrate.

EXAMPLES

Hereinafter, examples of the present invention will be more specificallydescribed. However, the present invention is not limited to thoseexamples.

Production Example 1 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-1 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 150 parts by mass ofpropylene glycol monomethylether acetate and 30 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced in the flask. The temperature of the solution was increasedto 80° C. Then, a mixture of 20 parts by mass of N-cyclohexyl maleimide,40 parts by mass of dicyclopentanyl methacrylate, 25 parts by mass of2-ethylhexyl methacrylate, 15 parts by mass of methacrylic acid, and 3parts by mass of 2,2′-azobis(isobutyronitrile) was added dropwise, andthe whole was stirred at 80° C. for 6 hours, whereby a solution of a(meth)acrylate polymer P-1 (solid content: 36 mass %) was obtained.

[Measurement of Acid Number]

The acid number of P-1 was measured and resulted in 98 mgKOH/g. Here,the acid number was calculated from the amount of a 0.1-mol/l aqueouspotassium hydroxide solution required for neutralizing the P-1 solution.At this time, a point at which phenolphthalein added as an indicatorcolored pink from colorless was defined as a point of neutralization.

[Measurement of Weight Average Molecular Weight]

The weight average molecular weight (in terms of standard polystyrene)of P-1 was 27,000 as a result of the measurement using GPC (manufacturedby Tosoh Corporation, SD-8022/DP-8020/RI-8020). Here, a column used wasGelpack GL-A150-S/GL-A160-S manufactured by Hitachi Chemical Co., Ltd.

Production Example 2 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-2 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 168 parts by mass (solidcontent: 60 mass %) of the above P-1 solution (solid content: 36 mass%), 0.03 part by mass of dibutyltin dilaurate, and 0.1 part by mass ofp-methoxyphenol were weighed and stirred while being aerated. Thetemperature of the solution was increased to 60° C. and 7 parts by massof 2-methacryloyl oxyethyl isocyanate was then added dropwise to thesolution over 30 minutes. After that, the solution was continuouslystirred at 60° C. for 4 hours, whereby a solution of a (meth)acrylatepolymer P-2 (solid content: 38 mass %) was obtained.

The acid number and weight average molecular weight of P-2 were 53mgKOH/g and 27,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 3 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-3 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 97 parts by mass ofpropylene glycol monomethylether acetate and 24 parts by mass of ethyllactate were weighed and then stirred while a nitrogen gas wasintroduced in the flask. The temperature of the solution was increasedto 90° C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide,43 parts by mass of dicyclopentanyl methacrylate, 53 parts by mass of2-hydroxyethyl methacrylate, 20 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 65 parts by mass ofpropylene glycol monomethylether acetate, and 16 parts by mass of ethyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour, whereby a solution of a (meth)acrylate polymer P-3 (solid content:40 mass %) was obtained.

The acid number and weight average molecular weight of P-3 were 96mgKOH/g and 25,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 4 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-4 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 150 parts by mass (solidcontent: 60 mass %) of the above P-3 solution (solid content: 40 mass%), 0.04 part by mass of dibutyltin dilaurate, 0.1 part by mass ofp-methoxyphenol, and 21 parts by mass of propylene glycolmonomethylether acetate were weighed and stirred while being aerated.The temperature of the solution was increased to 60° C. and 14 parts bymass of 2-methacryloyl oxyethyl isocyanate was then added dropwise tothe solution over 30 minutes. After that, the solution was continuouslystirred at 60° C. for 4 hours, whereby a solution of a (meth)acrylatepolymer P-4 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-4 were 57mgKOH/g and 25,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 5 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-5 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 94 parts by mass ofpropylene glycol monomethylether acetate and 24 parts by mass of ethyllactate were weighed and then stirred while a nitrogen gas wasintroduced in the flask. The temperature of the solution was increasedto 90° C. Then, a mixture of 33 parts by mass of N-cyclohexyl maleimide,26 parts by mass of dicyclopentanyl methacrylate, 51 parts by mass of2-hydroxyethyl methacrylate, 19 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 63 parts by mass ofpropylene glycol monomethylether acetate, and 16 parts by mass of ethyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour and then cooled to room temperature.

Subsequently, 0.08 part by mass of dibutyltin dilaurate, 0.2 part bymass of p-methoxyphenol, and 45 parts by mass of propylene glycolmonomethylether acetate were added and then stirred while being aerated.The temperature of the solution was increased to 60° C. and 30 parts bymass of 2-methacryloyl oxyethyl isocyanate was then added dropwise tothe solution over 30 minutes. After that, the solution was continuouslystirred at 60° C. for 4 hours, whereby a solution of a (meth)acrylatepolymer P-5 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-5 were 54mgKOH/g and 23,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 6 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-6 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 97 parts by mass ofpropylene glycol monomethylether acetate and 24 parts by mass of ethyllactate were weighed and then stirred while a nitrogen gas wasintroduced in the flask. The temperature of the solution was increasedto 90° C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide,43 parts by mass of benzil methacrylate, 53 parts by mass of2-hydroxyethyl methacrylate, 20 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 65 parts by mass ofpropylene glycol monomethylether acetate, and 16 parts by mass of ethyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour, whereby a solution of a (meth)acrylate polymer P-6 (solid content:40 mass %) was obtained.

The acid number and weight average molecular weight of P-6 were 96mgKOH/g and 24,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 7 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-7 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 150 parts by mass (solidcontent: 60 mass %) of the above P-6 solution (solid content: 40 mass%), 0.04 part by mass of dibutyltin dilaurate, 0.1 part by mass ofp-methoxyphenol, and 21 parts by mass of propylene glycolmonomethylether acetate were weighed and stirred while being aerated.The temperature of the solution was increased to 60° C. and 14 parts bymass of 2-methacryloyl oxyethyl isocyanate was then added dropwise tothe solution over 30 minutes. After that, the solution was continuouslystirred at 60° C. for 4 hours, whereby a solution of a (meth)acrylatepolymer P-7 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-7 were 58mgKOH/g and 24,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 8 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-8 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 60 parts by mass ofpropylene glycol monomethylether acetate and 60 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced in the flask. The temperature of the solution was increasedto 90° C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide,61 parts by mass of benzyl methacrylate, 18 parts by mass of2-hydroxyethyl methacrylate, 37 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 40 parts by mass ofpropylene glycol monomethylether acetate, and 40 parts by mass of methyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour and then cooled to room temperature.

Subsequently, 28 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 43 parts by mass of propylene glycolmonomethylether acetate were added and then stirred while being aerated.The temperature of the solution was increased to 80° C. and 0.7 part bymass of triphenyl phosphine was then added. After that, the solution wascontinuously stirred at 80° C. for 1 hour and furthermore at 110° C. for8 hours, whereby a solution of a (meth)acrylate polymer P-8 (solidcontent: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-8 were 78mgKOH/g and 25,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 9 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-9 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 60 parts by mass ofpropylene glycol monomethylether acetate and 60 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced therein. The temperature of the solution was increased to 90°C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide, 79parts by mass of benzyl methacrylate, 37 parts by mass of methacrylicacid, 2 parts by mass of 2,2′-azobis(isobutyronitrile), 40 parts by massof propylene glycol monomethylether acetate, and 40 parts by mass ofmethyl lactate was added dropwise over 3 hours, and the whole wasstirred at 90° C. for 3 hours. The solution was further stirred at 120°C. for 1 hour and then cooled to room temperature.

Subsequently, 28 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 43 parts by mass of propylene glycolmonomethylether acetate were added to the solution and then the wholewas stirred while being aerated. The temperature of the solution wasincreased to 80° C. and 0.6 part by mass of triphenyl phosphine was thenadded. After that, the solution was continuously stirred at 80° C. for 1hour and furthermore at 110° C. for 8 hours, whereby a solution of a(meth)acrylate polymer P-9 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-9 were 78mgKOH/g and 25,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 10 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-10 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 60 parts by mass ofpropylene glycol monomethylether acetate and 60 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced therein. The temperature of the solution was increased to 90°C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide, 53parts by mass of benzyl methacrylate, 37 parts by mass of methacrylicacid, 25 parts by mass of styrene, 2 parts by mass of2,2′-azobis(isobutyronitrile), 40 parts by mass of propylene glycolmonomethylether acetate, and 40 parts by mass of methyl lactate wasadded dropwise over 3 hours, and the whole was stirred at 90° C. for 3hours. The solution was further stirred at 120° C. for 1 hour and thencooled to room temperature.

Subsequently, 19 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 28 parts by mass of propylene glycolmonomethylether acetate were added to the solution, and then the wholewas stirred while being aerated. The temperature of the solution wasincreased to 80° C. and 0.6 part by mass of triphenyl phosphine was thenadded. After that, the solution was continuously stirred at 80° C. for 1hour and furthermore at 110° C. for 8 hours, whereby a solution of a(meth)acrylate polymer P-10 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-10 were 108mgKOH/g and 22,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 11 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-11 Containing Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 96 parts by mass ofpropylene glycol monomethylether acetate and 24 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced therein. The temperature of the solution was increased to 90°C. Then, a mixture of 18 parts by mass of N-cyclohexyl maleimide, 69parts by mass of 2-ethylhexyl methacrylate, 23 parts by mass of2-hydroxyethyl methacrylate, 24 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 64 parts by mass ofpropylene glycol monomethylether acetate, and 16 parts by mass of methyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour and then cooled to room temperature.

Subsequently, 19 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 28 parts by mass of propylene glycolmonomethylether acetate were added to the solution, and then the wholewas stirred while being aerated. The temperature of the solution wasincreased to 80° C. and 0.6 part by mass of triphenyl phosphine was thenadded. After that, the solution was continuously stirred at 80° C. for 1hour and furthermore at 110° C. for 8 hours, whereby a solution of a(meth)acrylate polymer P-11 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-11 were 54mgKOH/g and 26,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 12 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-12 Free of Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 60 parts by mass ofpropylene glycol monomethylether acetate and 60 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced therein. The temperature of the solution was increased to 90°C. Then, a mixture of 18 parts by mass of cyclohexyl methacrylate, 79parts by mass of benzyl methacrylate, 37 parts by mass of methacrylicacid, 2 parts by mass of 2,2′-azobis(isobutyronitrile), 40 parts by massof propylene glycol monomethylether acetate, and 40 parts by mass ofmethyl lactate was added dropwise over 3 hours, and the whole wasstirred at 90° C. for 3 hours. The solution was further stirred at 120°C. for 1 hour and then cooled to room temperature.

Subsequently, 28 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 43 parts by mass of propylene glycolmonomethylether acetate were added to the solution, and then the wholewas stirred while being aerated. The temperature of the solution wasincreased to 80° C. and 0.6 part by mass of triphenyl phosphine was thenadded. After that, the solution was continuously stirred at 80° C. for 1hour and furthermore at 110° C. for 8 hours, whereby a solution of a(meth)acrylate polymer P-12 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-12 were 78mgKOH/g and 27,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Production Example 13 Preparation of Alkali-Soluble (Meth)AcrylatePolymer P-13 Free of Maleimide Skeleton in Main Chain

In a flask equipped with an agitating device, a cooling pipe, a gasconduit, a dropping funnel, and a thermometer, 96 parts by mass ofpropylene glycol monomethylether acetate and 24 parts by mass of methyllactate were weighed and then stirred while a nitrogen gas wasintroduced therein. The temperature of the solution was increased to 90°C. Then, a mixture of 18 parts by mass of cyclohexyl methacrylate, 69parts by mass of 2-ethylhexyl methacrylate, 23 parts by mass of2-hydroxyethyl methacrylate, 24 parts by mass of methacrylic acid, 2parts by mass of 2,2′-azobis(isobutyronitrile), 64 parts by mass ofpropylene glycol monomethylether acetate, and 16 parts by mass of methyllactate was added dropwise over 3 hours, and the whole was stirred at90° C. for 3 hours. The solution was further stirred at 120° C. for 1hour and then cooled to room temperature.

Subsequently, 19 parts by mass of glycidyl methacrylate, 0.2 part bymass of p-methoxyphenol, and 28 parts by mass of propylene glycolmonomethylether acetate were added to the solution, and then the wholewas stirred while being aerated. The temperature of the solution wasincreased to 80° C. and 0.6 part by mass of triphenyl phosphine was thenadded. After that, the solution was continuously stirred at 80° C. for 1hour and furthermore at 110° C. for 8 hours, whereby a solution of a(meth)acrylate polymer P-13 (solid content: 40 mass %) was obtained.

The acid number and weight average molecular weight of P-13 were 54mgKOH/g and 25,000, respectively, as a result of measurement conductedby the same methods as those of Production Example 1.

Example 1 Preparation of Resin Varnish COV-1 for the Formation of CorePart

In a wide-mouthed polyethylene bottle, (A) 168 parts by mass (solidcontent: 60 parts by mass) of the above solution of P-1 (solid content:36 mass %) as an alkali-soluble (meth)acrylate polymer having amaleimide skeleton in a main chain, (B) 20 parts by mass of ethoxylatedbisphenol A diacrylate (A-BPE-6, manufactured by Shin-nakamura ChemicalCorporation) and 20 parts by mass of p-cumylphenoxyethyl acrylate(A-CMP-1E, manufactured by Shin-nakamura Chemical Corporation) aspolymerizable compounds, and (C) 1 part by mass of1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-on(Irgacure 2959, manufactured by Ciba Specialty Chemicals) and 1 part bymass of bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (Irgacure 819,manufactured by Ciba Specialty Chemicals) as polymerization initiatorswere weighed and then stirred for 6 hours using a stirring device at arotation speed of 400 rpm at a temperature of 25° C., whereby a resinvanish for the formation of a core part was prepared. After that, theresulting preparation was subjected to pressure filtration with apolyflon filter (PF020, manufactured by Advantec MFS, Inc.) with a poresize of 2 μm and a membrane filter (J050A, manufactured by Advantec MFS,Inc.) with a pore size of 0.5 μm at a temperature of 25° C. and apressure of 0.4 MPa. Subsequently, the preparation was defoamed using avacuum pump and a bell jar under reduced pressure for 15 minutes at areduced pressure of 50 mmHg, whereby a resin varnish COV-1 for theformation of a core part was obtained.

[Preparation of Resin Film COF-1 for the Formation of Core Part]

The above resin varnish COV-1 for the formation of a core part wasapplied onto the untreated surface of a PET film (A1517 of 16 μm inthickness, manufactured by Toyobo Co., Ltd.) with a coater (MulticoaterTM-MC, manufactured by Hirano Tecseed Co., Ltd.), dried at 100° C. for20 minutes, and attached with a releasable PET film (A31 of 25 μm inthickness, manufactured by Teijin DuPont Films Japan Limited), whereby aresin film COF-1 for the formation of a core part was obtained. In thiscase, the thickness of the resin layer can be optionally adjusted byadjusting the gap of the coater. In this example, the thickness wasadjusted so that the film thickness after the hardening could be 50 μm.

[Preparation of Resin Varnish CLV-1 for the Formation of Clad Layer]

In a wide-mouthed polyethylene bottle, 303 parts by mass (solid content:50 parts by mass) of a solution of acrylic rubber (HTR-860P-3,manufactured by Nagase ChemteX Corporation) with a molecular weight ofabout 850,000 in methyl ethyl ketone (sold content: 17 mass %) as abinder polymer, (B) 50 parts by mass of alicyclic diepoxycarboxylate(KRM-2110, manufactured by Adeka Corporation) as a polymerizablecompound, and (C) 4 parts by mass (solid content: 2 parts by mass) of asolution of triaryl sulfonium hexafluoroantimonate salt (SP-170,manufactured by Adeka Corporation) (solid content: 50 mass %) as apolymerization initiator were weighed and then stirred for 6 hours usinga stirring device at a rotation speed of 400 rpm at a temperature of 25°C., whereby a resin vanish for the formation of a clad layer wasprepared. After that, the resulting preparation was subjected topressure filtration with a polyflon filter (PF060, manufactured byAdvantec MFS, Inc.) with a pore size of 6 μm at a temperature of 25° C.and a pressure of 0.4 MPa. Subsequently, the preparation was defoamedusing a vacuum pump and a bell jar under reduced pressure for 15 minutesat a reduced pressure of 50 mmHg, whereby a resin varnish CLV-1 for theformation of a clad layer was obtained.

[Preparation of Resin Film CLF-1 for the Formation of Clad Layer]

The above resin varnish CLV-1 for the formation of a clad layer wasapplied onto the untreated surface of a PET film (A1517 of 16 μm inthickness, manufactured by Toyobo Co., Ltd.) and then dried in a mannersimilar to that of the resin film for the formation of a core layer,whereby a resin film CLF-1 for the formation of a clad layer wasobtained. In this case, the thickness of the resin layer can beoptionally adjusted by adjusting the gap of the coater. In this example,the thickness was adjusted so that the film thickness after thehardening could be 30 μm for the resin film for the formation of a lowerclad layer, 80 μm for the resin film for the formation of an upper cladlayer, and 50 μm for the hardened film for the measurement of refractiveindex and transmissivity.

[Preparation of Hardened Film for the Measurement of Refractive Indexand Transmissivity]

A UV ray (at a wavelength of 365 nm) at an intensity of 1,000 mJ/cm² wasapplied to the resin film for the formation of a core part and the resinfilm for the formation of a clad layer by using a UV exposure device(MAP-1200-L, manufactured by Dainippon Screen Mfg. Co., Ltd.).Subsequently, the protective film (A31) was removed and then theremainder was dried at 130° C. for 1 hour. After that, the base materialfilm (A1517) was removed, whereby a hardened film with a thickness of 50μm was obtained.

[Measurement of Refractive Index]

The refractive index of the obtained hardened film at a wavelength of830 nm at a temperature of 25° C. was measured using a prism coupler(SPA-4000, manufactured by Sairon Technology, Co., Ltd.). The measuredrefractive index was 1.524.

[Measurement of Transmissivity]

The transmissivity of the obtained hardened film at a wavelength of 400nm at a temperature of 25° C. was measured using a spectrophotometer(U-3410 spectrophotometer, manufactured by Hitachi Ltd.). The measuredtransmissivity was 87%.

[Preparation of Optical Waveguide]

The resin film CLF-1 for the formation of a lower clad layer from whichthe protective film (A31) had been removed was laminated on an FR-4substrate (E-679FB, manufactured by Hitachi Chemical Co., Ltd.) using aroll laminator (HLM-1500, manufactured by Hitachi Plant Techno Co.,Ltd.) under the conditions of a pressure of 0.4 MPa, a temperature of80° C., and a rate of 0.4 m/min. Further, pressure-bonding was performedusing a vacuum-pressure type laminator (MVLP-500/600, manufactured byMeiki Co., Ltd.) under the conditions of a pressure of 0.5 MPa, atemperature of 50° C., and a pressure time of 30 seconds.

Next, the base material film (A1517) was removed after the applicationof a UV ray (at a wavelength of 365 nm) at an intensity of 1,000 mJ/cm²by using a UV exposure device (MAP-1200-L, manufactured by DainipponScreen Mfg. Co., Ltd.), and then the remainder was subjected to a heattreatment at 120° C. for 1 hour, whereby an under clad layer 4 wasformed.

Subsequently, the resin film COF-1 for the formation of a core part fromwhich the protective film (A31) had been removed was laminated on thelower clad layer 4 using the above roll laminator under the conditionsof a pressure of 0.4 MPa, a temperature of 80° C., and a rate of 0.4m/min. Further, pressure-bonding was performed using the abovevacuum-pressure type laminator under the conditions of a pressure of 0.5MPa, a temperature of 50° C., and a pressure time of 30 seconds.

Subsequently, the resultant was irradiated with the UV ray (at awavelength of 365 nm) at an intensity of 500 mJ/cm² by using the aboveexposure device through a photo mask (negative type) of 50 μm in widthand then exposed at 80° C. for 5 minutes, followed by heating. The basematerial film (A1517) was removed and the core part 2 was then developedusing a developer (2.38-mass % aqueous tetramethylammonium hydroxidesolution). After that, the core part 2 was washed with pure filter andthen dried by heating at 100° C. for 1 hour.

Subsequently, the resin film CLF-1 for the formation of an upper cladlayer from which the protective film (A31) had been removed waslaminated on the core part 2 and the lower clad layer 4 using the abovevacuum-pressure type laminator under the conditions of a pressure of 0.5MPa, a temperature of 50° C., and a pressure time of 30 seconds. Theresultant was irradiated with the UV ray (at a wavelength of 365 nm) atan intensity of 2,000 mJ/cm², and the base material film (A1517) wasremoved. After that, the remainder was subjected to a heat treatment at120° C. for 1 hour. As a result, an upper clad layer 3 was formed and anoptical waveguide having a substrate 5 as shown in FIG. 1( a) wasobtained. Subsequently, the optical waveguide was cut into pieces of 5cm in waveguide length using a dicing saw (DAD-341, manufactured byDISCO Inc.).

[Measurement of Optical Transmission Loss]

The optical transmission loss of each cutout optical waveguide was 0.18dB/cm as a result of measurement by a cutback method (measured waveguidelengths of 5, 3, and 2 cm) using a VCSEL (FLS-300-01-VCL, manufacturedby EXFO Co, Ltd.) (light at a wavelength of 850 nm as a centerwavelength) as alight source, a light-receiving sensor (Q82214,manufactured by Advantest Corporation), a light-incidence fiber(GI-50/125 multi-mode fiber, NA=0.20), and an light-output fiber(SI-114/125, NA=0.22).

[Reflow Test]

A cutout optical waveguide (a waveguide length of 5 cm) was subjected toa reflow test three times using a reflow tester (Salamander XNA-645PC,manufactured by Furukawa electric Co., Ltd.) at a maximum temperature of265° C. under the conditions based on IPC/JEDEC J-STD-020B. The detailedreflow conditions are listed in Table 1, and the temperature profile inthe reflow furnace is represented in FIG. 2.

TABLE 1 Zone No. 1 2 3 4 5 6 7 Upper heater preset 175 195 220 250 280220 0 temperature (° C.) Lower heater preset 175 195 220 250 300 240 —temperature (° C.) Conveyer speed 60 (cm/min)

The insertion loss of a flexible optical waveguide after the reflow testwas 0.28 dB/cm as a result of measurement using the same light source,light-receiving device, incidence fiber, and output fiber as thosedescribed above.

Examples 2 to 10 and Comparative Example 1

Resin varnishes for the formation of a core part, COV-2 to 9, wereprepared according to the respective blending ratios shown in Table 2.Likewise, resin varnishes for the formation of a clad layer, CLV-2 to 8,were prepared according to the respective blending ratios shown in Table3. In a manner similar to Example 1, resin films for the formation of acore part, COF-2 to 9, and resin films for the formation of a cladlayer, CLF-2 to 8, were prepared and optical waveguides 1 were thenprepared, respectively. Table 4 shows each combination of the resin filmfor the formation of a core part and the resin film for the formation ofa clad layer used in the production of the optical waveguide 1. Inaddition, Table 5 shows the results of the measurement of: therefractive index and transmissivity of the obtained hardened film; andthe transmission losses of the optical waveguide 1 before and after thereflow test.

TABLE 2 Item Mixed component COV-1 COV-2 COV-3 COV-4 COV-5 (A) P-1solution*¹ 168 — — — — (Meth)acrylate (solid content: 36 mass %) (solidpolymer (part by content 60) mass) P-3 solution*² — 150 — — — (solidcontent: 40 mass %) (solid content 60) P-4 solution*³ — — 150 — — (solidcontent: 40 mass %) (solid content 60) P-6 solution*⁴ — — — 150 — (solidcontent: 40 mass %) (solid content 60) P-7 solution*⁵ — — — — 150 (solidcontent: 40 mass %) (solid content 60) P-8 solution*⁶ — — — — — (solidcontent: 40 mass %) P-9 solution*⁷ — — — — — (solid content: 40 mass %)P-10 solution*⁸ — — — — — (solid content: 40 mass %) P-12 solution*⁹ — —— — — (solid content: 40 mass %) (B) A-8PE-6*¹⁰ 20 20 20 — 20Polymerizable EA-0500*¹¹ — — — 20 — compound A-CMP-1E*¹² 20 20 20 20 —(part by mass) A-401P*¹³ — — — — 20 (C) Irgacure 2959*¹⁴ 1 1 1 1 1Polymerization initiator (part by mass) Irgacure I-819*¹⁵ 1 1 1 1 1Resin film for the formation of core part COF-1 COF-2 COF-3 COF-4 COF-5Item Mixed component COV-6 COV-7 COV-8 COV-9 (A) P-1 solution*¹ — — — —(Meth)acrylate (solid content: 36 mass %) polymer (part by mass) P-3solution*² — — — — (solid content: 40 mass %) P-4 solution*³ — — — —(solid content: 40 mass %) P-6 solution*⁴ — — — — (solid content: 40mass %) P-7 solution*⁵ — — — — (solid content: 40 mass %) P-8 solution*⁶150 — — — (solid content: 40 mass %) (solid content 60) P-9 solution*⁷ —150 — — (solid content: 40 mass %) (solid content 60) P-10 solution*⁸ —— 150 — (solid content: 40 mass %) (solid content 60) P-12 solution*⁹ —— — 150 (solid content: 40 mass %) (solid content 60) (B) A-8PE-6*¹⁰ 2020 20 20 Polymerizable EA-0500*¹¹ — — — — compound A-CMP-1E*¹² — 20 20 —(part by mass) A-401P*¹³ 20 — — 20 (C) Irgacure 2959*¹⁴ 1 1 1 1Polymerization initiator (part by mass) Irgacure I-819*¹⁵ 1 1 1 1 Resinfilm for the formation of core part COF-6 COF-7 COF-8 COF-9*¹(Meth)acrylate polymer solution produced in Production Example 1*²(Meth)acrylate polymer solution produced in Production Example 3*³(Meth)acrylate polymer solution produced in Production Example 4*⁴(Meth)acrylate polymer solution produced in Production Example 6*⁵(Meth)acrylate polymer solution produced in Production Example 7*⁶(Meth)acrylate polymer solution produced in Production Example 8*⁷(Meth)acrylate polymer solution produced in Production Example 9*⁸(Meth)acrylate polymer solution produced in Production Example 10*⁹(Meth)acrylate polymer solution produced in Production Example 12*¹⁰Ethoxylated bisphenol A diacrylate (manufactured by Shin-nakamuraChemical Corporation) *¹¹Ethoxylated fluorene-type diacrylate(manufactured by Osaka Gas Chemicals Co., Ltd.) *¹²p-cumylphenoxyethylacrylate (manufactured by Shin-nakamura Chemical Corporation)*¹³2-hydroxy-3-(o-phenylphenoxy)propylacrylate (manufactured byShin-nakamura Chemical Corporation)*¹⁴1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(manufactured by Ciba Specialty Chemicals)*¹⁵Bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (manufactured by CibaSpecialty Chemicals)

TABLE 3 Item Mixed component CLV-1 CLV-2 CLV-3 CLV-4 (A) P-2 solution*¹— 150 — — (Meth)acrylate (solid content: 36 mass %) (Solid polymer (partby content 60) mass) P-4 solution*² — — 150 150 (solid content: 40 mass%) (Solid (Solid content 60) content 60) P-5 solution*³ — — — — (solidcontent: 40 mass %) P-11 solution*⁴ — — — — (solid content: 40 mass %)P-13 solution*⁵ — — — — (solid content: 40 mass %) (B) A-9300*⁶ — 20 20— Polymerizable EA-5420*⁷ — 20 — 20 compound A-CHD-4E*⁸ — — 20 20 (partby mass) M-215*⁹ — — — — KRM-2110*¹⁰ 50 — — — (C) Irgacure 2959*¹¹ — 1 11 Polymerization Irgacure 819*¹² — 1 1 1 initiator SP-170*¹³ solution 4— — — (part by mass) (solid content: 50 mass %) (Solid content 2) (D)Other (part by HTR-860-3P*¹⁴ solution 303 — — — mass) (solid content: 17mass %) (Solid content 50) Resin film for the formation of clad layerCLF-1 CLF-2 CLF-3 CLF-4 Item Mixed component CLV-5 CLV-6 CLV-7 CLV-8 (A)P-2 solution*¹ — — — — (Meth)acrylate (solid content: 36 mass %) polymer(part by mass) P-4 solution*² — — — — (solid content: 40 mass %) P-5solution*³ 150 — — — (solid content: 40 mass %) (Solid content 60) P-11solution*⁴ — 150 150 — (solid content: 40 mass %) (Solid (Solid content60) content 60) P-13 solution*⁵ — — — 150 (solid content: 40 mass %)(Solid content 60) (B) A-9300*⁶ 20 20 20 20 Polymerizable EA-5420*⁷ — —— — compound A-CHD-4E*⁸ 20 20 — 20 (part by mass) M-215*⁹ — — 20 —KRM-2110*¹⁰ — — — — (C) Irgacure 2959*¹¹ 1 1 1 1 Polymerization Irgacure819*¹² 1 1 1 1 initiator SP-170*¹³ solution — — — — (part by mass)(solid content: 50 mass %) (D) Other (part by HTR-860-3P*¹⁴ solution — —— — mass) (solid content: 17 mass %) Resin film for the formation ofclad layer CLF-5 CLF-6 CLF-7 CLF-8 *¹(Meth)acrylate polymer solutionproduced in Production Example 2 *²(Meth)acrylate polymer solutionproduced in Production Example 4 *³(Meth)acrylate polymer solutionproduced in Production Example 5 *⁴(Meth)acrylate polymer solutionproduced in Production Example 11 *⁵(Meth)acrylate polymer solutionproduced in Production Example 13 *⁶Ethoxylated isocyanuric acidtriacrylate (manufactured by Shin-nakamura Chemical Corporation)*⁷Hydrogenated bisphenol A-type epoxyacrylate (manufactured byShin-nakamura Chemical Corporation) *⁸Ethoxylated cyclohexane dimethanoldiacrylate (manufactured by Shin-nakamura Chemical Corporation)*⁹Ethoxylated isocyanuric acid diacrylate (manufactured by TOAGOSEI CO.,LTD.) *¹⁰Alicyclic diepoxycarboxylate (manufactured by AdekaCorporation)*¹¹1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(manufactured by Ciba Specialty Chemicals)*¹²Bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (manufactured by CibaSpecialty Chemicals)*¹³Triarylsulfoniumhexafluoroantimonatesalt(manufactured by AdekaCorporation) *¹⁴Acrylic rubber (manufactured by Nagase ChemteXCorporation.)

TABLE 4 Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Resin film for the CLF-1 CLF-2 CLF-3 CLF-4 CLF-3 CLF-5 formation oflower clad layer Resin film for the COF-1 COF-2 COF-3 COF-3 COF-4 COF-5formation of core part Resin film for the CLF-1 CLF-2 CLF-3 CLF-4 CLF-3CLF-5 formation of upper clad layer Comparative Item Example 7 Example 8Example 9 Example 10 Example 1 Resin film for the CLF-6 CLF-7 CLF-1CLF-7 CLF-8 formation of lower clad layer Resin film for the COF-6 COF-7COF-7 COF-8 COF-9 formation of core part Resin film for the CLF-6 CLF-7CLF-1 CLF-7 CLF-8 formation of upper clad layer

TABLE 5 Item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Resin film Film COF-1 COF-2 COF-3 COF-3 COF-4 COF-5 for the formationReflective 1.524 1.525 1.527 1.527 1.541 1.535 of core part index*¹Transmissivity 87 86 87 87 83 86 (%)*² Resin film Film CLF-1 CLF-2 CLF-3CLF-4 CLF-3 CLF-5 for the formation Reflective 1.496 1.507 1.509 1.5061.509 1.510 of clad layer index*¹ Transmissivity 63 90 91 89 91 90 (%)*²Optical Initial 0.18 0.12 0.12 0.11 0.19 0.15 waveguide transmissionloss (dB/cm) Transmission 0.28 0.24 0.20 0.21 0.26 0.23 loss afterperformance of reflow test three times (dB/cm) Comparative Item Example7 Example 8 Example 9 Example 10 Example 1 Resin film Film COF-6 COF-7COF-7 COF-8 COF-9 for the formation Reflective 1.540 1.539 1.539 1.5461.538 of core part index*¹ Transmissivity 86 87 87 83 87 (%)*² Resinfilm Film CLF-6 CLF-7 CLF-1 CLF-7 CLF-8 for the formation Reflective1.505 1.506 1.496 1.506 1.504 of clad layer index*¹ Transmissivity 91 9063 90 90 (%)*² Optical Initial 0.14 0.12 0.13 0.16 0.14 waveguidetransmission loss (dB/cm) Transmission 0.23 0.19 0.24 0.21 0.35 lossafter performance of reflow test three times (dB/cm) *¹a wavelength of830 nm, 25° C., and a film thickness of 50 μm *²a wavelength of 400 nm,25° C., and a film thickness of 50 μm

1. A method for preparing an optical waveguide, which comprises thesteps of: (1) providing a resin composition for an optical materialcomprising (A) at least one of an alkali-soluble acrylate polymer and analkali-soluble methacrylate polymer, each containing a maleimideskeleton in a main chain, (B) a polymerizable compound, and (C) apolymerization initiator; (2) forming with the resin composition atleast one layer of a lower clad layer, a core part, and an upper cladlayer; and (3) developing the above-formed layer with an aqueousalkaline solution.
 2. The method for preparing an optical waveguideaccording to claim 1, wherein the main chains of (A) the alkali-solubleacrylate polymer and the alkali-soluble methacrylate polymer includerepeating units (A-1) and (A-2) represented respectively by thefollowing general formulae (1) and (2) and at least one of repeatingunits (A-3) and (A-4) represented respectively by the following generalformulae (3) and (4):

where R¹ to R³ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms;

where R⁴ to R⁶ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms, and R⁷ represents anorganic group having 1 to 20 carbon atoms;

where R⁷ to R⁹ each independently represent any of a hydrogen atom andan organic group having 1 to 20 carbon atoms;

where R¹⁰ to R¹² and X¹ each independently represent any of a hydrogenatom and an organic group having 1 to 20 carbon atoms.
 3. The method forpreparing an optical waveguide according to claim 1, wherein (B) thepolymerizable compound comprises at least one of compounds representedby the following general formulae (5) to (8):

where: Ar represents any of the following groups;

X² represents any of divalent groups of an oxygen atom (O), a sulfuratom (S), OCH₂, SCH₂, O(CH₂CH₂O)_(a), O[CH₂CH(CH₃)O]_(b), andOCH₂CH(OH)CH₂O; Y¹ represents any of the following divalent groups;

R¹³ represents any of a hydrogen atom and a methyl group; R¹⁴ to R³⁰each independently represent any of a hydrogen atom, a fluorine atom, anorganic group having 1 to 20 carbon atoms, and a fluorine-containingorganic group having 1 to 20 carbon atoms; and a and b eachindependently represent an integer of 1 to 20, and c represents aninteger of 2 to 10;

where: R³¹ represents any of the following groups;

R³² to R³⁴ each independently represent any of a hydrogen atom and amethyl group; and d represents an integer of 1 to 10;

where: X³ and X⁴ each independently represent any of divalent groups ofO, S, O(CH₂CH₂O)_(e), and O[CH₂CH(CH₃)O]_(f); Y² represents any of thefollowing divalent groups;

R³⁵ and R⁴⁰ each independently represent any of a hydrogen atom and amethyl group; R³⁶ to R³⁹ each independently represent any of a hydrogenatom, a fluorine atom, an organic group having 1 to 20 carbon atoms, anda fluorine-containing organic group having 1 to 20 carbon atoms; and eand f each independently represent an integer of 1 to 20, and grepresents an integer of 2 to 10;

where: Y³ represents any of the following divalent groups;

R⁴¹ and R⁴⁶ each independently represent any of a hydrogen atom and amethyl group; R⁴² to R⁴⁵ each independently represent any of a hydrogenatom, a fluorine atom, an organic group having 1 to 20 carbon atoms, anda fluorine-containing organic group having 1 to 20 carbon atoms; and hrepresents an integer of 1 to 5, and i represents an integer of 2 to 10.4. The method for preparing an optical wave guide according to claim 1,wherein a core part is formed of the resin composition.